Anatomy – Exam 3

Organization of the Neck ○ Objectives

Organization of the neck: describe the cervical fascia and compartments

Describe the cervical regions/triangles. What are their boundaries and contents

What structures are found in the “key vertebral levels” in the neck?

Muscles of the neck, describe the neck muscles. Know their innervation, attachments and primary actions

○ Cervical Fascia

Superficial – contains fat, nerves, vasculature and platysma muscle

Deep

Investing Fascia – around just about everything, goes on both sides of the SCM and trapezius

○ Goes from chin to hyoid, to manubrium

Pretracheal Space – between investing and pretracheal fascia starting just above the manubrium

○ Contains thyroid and is continuous with thorax anterior to the pericardium

Pretracheal Fascia - in front or around trachea, blends with fibrous pericardium

○ Visceral Layer - goes around trachea

Buccopharyngeal Portion – lines the posterior portion of the trach?ea

Contents – esophagus, pharynx, larynx, thyroid glands, parathyroid glands

Makes Visceral Compartment

○ Muscular Layer – covers the muscles between the trachea and the carotids (The 'SOS' muscles)

Prevertebral Fascia – goes around most of the muscles associated with the vertebra in the neck

○ Makes Vertebral Compartment

○ Contains cervical vertebrae, spinal cord, cervical nerves, cervical muscles

Carotid Sheath – goes around the internal jugular vein, common carotid artery, internal carotid and the

vagus nerve

○ Note – does not go around external carotid artery

Retropharyngeal Space – between buccopharyngeal fascia and prevertebral fascia

○ Opens into posterior or superior mediastinum

○ Spread of infection into this area can cause dysphagia (difficulty swallowing) or dysarthria (speaking)

Layers from Spine to Buccopharyngeal Fascia

Anterior longitudinal ligament (along spine) → Longus colli muscle → Prevertebral fascia →

retropharyngeal space → buccopharyngeal fascia → (pharyngeal muscle)

○ Key Vertebral Levels

C3 – Hyoid bone

C4 – Carotid bifurcation (into external and internal)

C4-5 – Thyroid cartilage (adam‟s apple)

C5 – Cricoid cartilage

C5-6 – inferior limit of pharynx and larynx; Superior limit of trachea and esophagus

Contains indentation between cricoid cartilage and 1st tracheal ring

C6-T1 – thyroid gland

○ SUPERFICIAL FASCIA

Contents Platysma

Anterior & external jugular veins

Cutaneous branches of cervical plexus

Cervical branch of facial nerve (CN VII)

○ DEEP FASCIA

Investing

Surrounds entire neck deep to skin and subcutaneous fascia

Encloses trapezius, SCM, and parotid and submandibular glands

Superior: blends with fascia of skull (including mandible) &

hyoid

Inferior: extends to manubrium, clavicle & scapula

Posterior: continuous with nuchal ligament to C7 spinous

process

Forms roof of cervical triangles

CN XI may adhere to deep surface of this fascia

Pretracheal

In anterior part of neck: visceral and muscular parts

Visceral part: encloses neck viscera (thyroid; parathyroids;

trachea; pharynx, and esophagus)

Superiorly: attaches to hyoid bone

Inferiorly: blends with fibrous pericardium

Laterally: blends with carotid sheath

Buccopharyngeal fascia: subdivision of pretracheal fascia

posterior to pharynx & esophagus

Forms anterior boundary of retropharyngeal space

Visceral part: encloses infrahyoid muscles

Retropharyngeal space

Potential space between buccopharyngeal fascia &

prevertebral fascia

Extends from base of skull into thorax

Function: facilitates movement of cervical viscera against

vertebral column

Route for spread of infection (e.g., from nasopharyngeal

tonsils)

Prevertebral

Surrounds vertebral column and its muscles

Lateral: forms axillary sheath

Superior: attaches to base of skull

Inferior: blends with anterior longitudinal ligament

Forms floor of posterior triangle and posterior

boundary of retropharyngeal space

Sympathetic chain in/on anterior aspect of this fascia

Carotid sheath

Neurovascular compartment at lateral edge of

retropharyngeal space

Contents CCA, ICA, and IJV, Vagus nerve (CN X),

Carotid sinus & body, Sympathetic fibers, Deep cervical lymph nodes

○ Regions

Lateral Cervical Region (Posterior Cervical Triangle)

Boundaries

○ Anterior – SCM

○ Posterior – Trapezius

○ Inferior – middle 1/3 of clavicle

○ Roof – investing fascia

○ Floor – muscles covered by prevertebral fascia (splenius capitus, levator scapulae, scalenes)

Divisions of Lateral Cervical Region

○ Occipital (rostral)/Subclavian Triangles – divided by the inferior belly of the omohyoid

○ Safe/Dangerous Areas – divided by accessory nerve (CN XI)

Contents

○ ○ Muscles – floor muscles (splenius capitis, levator scapulae, middle scalene, posterior scalene), and

inferior belly of omohyoid

○ Arteries – transverse cervical, suprascapular, 3rd

part of subclavian, and occipital arteries

○ Veins – Subclavian vein (receives external jugular)

External Jugular and branches (transverse cervical, suprascapular and anterior jugular veins)

○ Nerves – accessory nerve, roots of brachial plexus, suprascapular, phrenic nerves and

Cervical Plexus (C1-4) – the cutaneous branches

○ Lesser Occipital (C2) – travels superiorly

○ Greater Auricular (C2-3) – goes over SCM muscle vertically

○ Transverse Cervical (C2-3) – goes over SCM muscle horizontally

○ Supraclavicular nerves (C3-4) – goes along the external jugular vein inferiorly

Note – the external jugular vein goes over the SCM muscle

Anterior Cervical Region

Boundaries

○ Anterior – anterior midline of

neck

○ Posterior – SCM

○ Superior – mandible

Divisions

○ Submental (unpaired) – bounded

by anterior bellies of digastric

muscles and the hyoid bone

Floor – mylohyoid muscles

Contains submental lymph

nodes, and small veins

(tributaries of anterior jugular

vein)

○ Submandibular (paired) – bounded by mandible and anterior & posterior bellies of digastric muscles

Floor – mylohyoid muscle, hyoglossus muscle, middle pharyngeal constrictor muscle

Contains submandibular gland, submandibular lymph nodes, mylohyoid nerve, hypoglossal nerve

(CN XII), parts of fascial artery and vein

Glandular

○ Carotid Triangle (paired) – bounded by superior belly of omohyoid, posterior belly of digastric and

SCM

Floor – inferior pharyngeal constrictor muscle

Contents

○ Common carotid, internal carotid, external carotid (and branches) arteries

○ Carotid body and sinus

○ Internal jubular vein and tributaries

○ Deep cervical lymph nodes

○ Vagus, hypoglossal, and accessory nerves

○ Branches of the cervical plexus ○ Larynx and pharynx

○ Thyroid and parathyroid glands

Vascular

○ Muscular (paired) – bounded by superior belly of omohyoid, SCM and midline of neck

Contains infrahyoid muscles, thyroid and parathyroid glands

○ Neck Muscles

Note – there is an intermediate tendon that goes around the stylohyoid and diagastric muscles

Infrahyoid

Note – sternohyoid and omohyoid muscles are long

„SOS‟ – sternohyoid, omohyoid, sternothyroid muscles are innervated by ansa cervicalis

Note – omohyoid becomes tendinous (intermediate tendon) between its two bellies

These help stabilize hyoid and help with swallowing

Note – Scalenes have origin on TVP and insert on the ribs

Lateral flexors of neck and accessory respiratory muscles

Interscalene Space – between anterior and middle scalene muscles

Lets the brachial plexus and subclavian artery through

MUSCLE (GROUP) INNERVATION ORIGIN INSERTION ACTION(S)

SUPRAHYOID

Digastric Ant: CN V (Mylohyoid n.)

Post: CN VII

Ant: Digastric fossa

Post: Mastoid process

Hyoid bone (via intermediate tendon)

Depresses mandible, elevates hyoid bone

Stylohyoid CN VII Styloid process Hyoid bone Elevates & retracts hyoid bone; elongates floor of mouth

Mylohyoid CN V

(Mylohyoid n.)

Mylohyoid line (mandible)

Hyoid bone Elevates hyoid bone, & floor of mouth & tongue

Geniohyoid C1 (via CN XII) Mandible

(inf. mental spine)

Hyoid bone Elevates hyoid bone, shortens floor of mouth, widens pharynx

INFRAHYOID (S-O-S + T)

Sternohyoid (S) C1-3 (ansa cervicalis) Manubrium & Clavicle Hyoid bone Depresses hyoid bone

Omohyoid (O) C1-3 (ansa cervicalis) Scapula Hyoid bone Depresss & retracts hyoid bone

Sternothyroid (S) C1-3 (ansa cervicalis) Sternum Thyroid cartilage Depresses hyoid bone & larynx

Thyrohyoid C1 (via CN XII) Thyroid cartilage Hyoid body & greater horn Depresses hyoid bone & elevates larynx

LATERAL (DEEP) NECK MUSCLES

Anterior scalene Cervical ventral rami TVP C3-6 Rib 1 Elevates Rib 1, laterally flexes & rotates neck

Middle scalene Cervical ventral rami TVP C1-6 Rib 1 Laterally flexes neck, elevates rib 1 during forced inspiration

Posterior scalene Cervical ventral rami TVP C4-6 Rib 2 Laterally flexes neck, elevates rib 2 during forced inspiration

PREVERTEBRAL MUSCLES

Longus capitis Cervical plexus TVP C3-6 Occipital bone (basilar part) Acting bilaterally:

Flexes head

Longus colli Cervical plexus Body C1-3

TVP C3-6

Body C5-T3

TVP C3-5

Acting bilaterally:

Flexes neck

Acting unilaterally:

Rotates neck to opposite side

SUPERFICIAL MUSCLES

Platysma CN VII Superficial fascia over deltoid and pectoralis major

Mandible (lower border) & superficial fascia of lower face

Draws corner of mouth inferiorly, draws skin of neck superiorly

Sternocleidomastoid CN XI spinal part (motor),

C2-3 (pain & proprioception)

Manubrium & clavicle (two heads)

Mastoid process & superior nuchal line

Acting unilaterally: Laterally flexes & rotates head to opposite side

Acting bilaterally: Flexes neck

Trapezius CN XI spinal part C3-4 (pain & proprioception)

Occipital bone, lig. nuchae & spinous processes

Scapula and clavicle Elevates, retracts, & rotates scapula to tilt glenoid cavity superiorly

Nerves and Vessels of the Neck ○ Objectives

Blood Vessels

Describe the venous drainage of the neck. What is the relationship between the internal jugular vein and the carotid sheath? Where is the external jugular vein located?

Describe the branches of the external carotid artery. Are there branches of the internal carotid artery in the neck?

Describe the carotid body and carotid sinus

Nerves and Plexuses

Describe the cervical and branchial plexuses in the neck. Cervical plexus (ventral rami C1-C4) cutaneous nerves, ansa cervicalis

(C1-3) and phrenic nerve (C3-5). Brachial plexus (ventral rami C5-T1)

Describe the cranial nerves that course through and/or supply the neck: glossopharyngeal nerve, vagus nerve, accessory nerve,

hypoglossal nerve

Describe the cervical sympathetic trunk, its ganglia and branches

○ Veins of the Neck

Retromandibular Vein – drains into external jugular

Main tributaries

○ Superficial Temporal vein –

○ Maxillary veins – drains the pterygoid plexus (which is

deep to mandible)

External Jugular Vein – is in superficial fascia

Main tributaries (superiorly)

○ Retromandibular vein -

○ Posterior Auricular vein – from behind the ear

Other tributaries (inferiorly)

○ Anterior Jugular vein – is medial to the SCM

○ Transverse Cervical vein –

○ Suprascapular vein –

Terminates on Subclavian vein

Internal Jugular Vein – receives blood from brain

Main Tributaries – most come in anteriorly

○ Sigmoid Sinus – a continuation of IJV receiving brain blood

○ Inferior Petrosal Sinus – comes in anteriorly

○ Occipital Vein – comes in posteriorly

○ Pharyngeal Veins –

○ Common Facial Vein –

○ Lingual Vein –

○ Superior and Middle Thyroid Veins – supply thyroid

Unites with Subclavian to create the brachiocephalic vein

Just before the union with subclavian there is a bicuspid valve

that prevents backflow

○ External Carotid Artery (ECA)

Note – internal carotid doesn‟t branch in the neck

Note – external carotid artery isn’t in the carotid sheath

„SALFOAMS‟ when naming branches inferior to superior

Superficial Temporal Artery – supplies parotid & temporal regions

of skull

Can take a pulse here

Maxillary – supplies tissues around maxilla

Posterior Auricular – supplies tissues around external ear

Occipital – supplies posterior scalp and SCM

Facial – supplies face; ends in angular artery

Can take pulse, right at jaw line where it comes over mandible

Lingual – supplies tongue & floor of mouth

Can share common branch with facial artery

Ascending Pharyngeal Artery – supplies pharynx and SCM

Superior Thyroid Artery – supplies thyroid gland, SCM, infrahyoid muscles, part of larynx

○ Carotid Body & Carotid Sinus

Carotid Sinus Carotid Body

Location Dilation at bifurcation Ovoid mass at bifurcation

Receptors Baroreceptors Chemoreceptors

Response Reacts to ↑ arterial pressure

changes to ↓ HR

Reacts to ↓ O2 or ↑ CO2 → ↑ rate and

depth of respiration, ↑ HR, ↑ BP

Innervation Carotid Sinus Nerve – branch of glossopharyngeal (CN IX)

Secondary – vagus (provides parasympathetic vasodilation)

Secondary – cervical sympathetics (provide sympathetic vasoconstriction)

○ Cervical Plexus

Made of ventral rami of C1-C4

Motor Innervation

Hypoglossal Nerve (CN XII) – not part of cervical plexus

○ Innervates – tongue, geniohyoid and thyrohyoid

C1 Fibers – travel with hypoglossal nerve after coming off of C1

○ Thyrohyoid Nerve, Geniohyoid Nerve

Ansa Cervicalis (C1-C3) – „goose neck‟; lies on carotid sheath; „SOS‟

○ Has inferior root and superior root

○ Supplies the infrahyoid muscles and deep neck muscles

○ Sternohyoid Nerve, Omohyoid Nerve, Sternothyroid Nerve

Sensory Innervation

Ventral Rami – supply skin of anterior and lateral neck

○ Lesser Occipital (C2) – innervates neck and scalp posterosuperior

to auricle

○ Great Auricular (C2-3) – skin over parotid gland; posterior aspect

of auricle; between angle of mandible & mastoid process

○ Transverse Cervical (C2-3) – anterior cervical region

○ Supraclavicular (C3-4) – neck and shoulder

Dorsal Rami – supplies skin of posterior head and neck

○ Suboccipital (C1) –

○ Greater Occipital (C2) –

○ Third Occipital Nerve (C3) –

○ Cranial Nerves of the Neck

Glossopharyngeal (CN IX) – medial to vagus nerve

There is a bunch of extra info he didn‟t cover

Vagus (CN X) – in carotid sheath

There is a bunch of extra info he didn‟t cover

Supplies all the intrinsic laryngeal muscles (muscles of speech)

Superior Laryngeal Nerve – branch of vagus nerve

○ Internal Branch – penetrates the thyrohyoid membrane to be sensory to mucosa of larynx

○ External Branch – motor to cricothyroid muscle (a laryngeal muscle)

○ Note that there is a Superior Laryngeal Artery (branch of superior thyroid) that follows the superior

laryngeal nerve

Recurrent Laryngeal Nerve – goes around an artery then goes superiorly in the tracheoesophageal

groove

○ Motor to all intrinsic laryngeal muscles, except the cricothyroid

○ Right Recurrent Laryngeal – goes under subclavian

○ Left Recurrent Laryngeal – goes under aortic arch

Accessory Nerve (CN XI) – has two very different parts

Spinal Part – motor to SCM and trapezius

○ Fibers originate in cervical spinal cord (C1-5) and form spinal root of CN XI which ascends between the

dorsal and ventral roots then exits through jugular foramen

Cranial Part – motor fibers originate in brainstem, but eventually join up with CN X

○ Fibers join with spinal part of CN XI to exit through the jugular foramen, then split off to join CN X

○ Muscle Supplied – soft palate, pharynx, intrinsic laryngeal muscles, palatoglossus

○ Cervical Sympathetic Trunk and Ganglia????????????????

Anterolateral to vertebral column

Covered by prevertebral fascia

Presynaptic Cells – come from lateral horn of thoracic spinal cord

T1-3 – head and salivary glands

T1-2 – eye

Presynaptic Fibers – get to sympathetic trunk via thoracic spinal nerves and white rami

Fibers then synapse in a cervical ganglia (inferior, middle, superior)

Note – there aren‟t any white rami in the cervical region because the fibers come from thoracic region

Postsynaptic Fibers – leave via gray rami to join cervical spinal nerves

Cardiopulmonary splanchnic nerves – supply thoracic viscera

Use sympathetic plexi?

Superior Cervical Ganglion (C1-2) – large ganglion posterior to ICA

Postsynaptic Fibers????????????????

○ ICA plexus enters cranial cavity to supply cranial vasculature and other structures

○ Contributes fibers to ECA branches

○ Gray rami to C1-4 spinal nerves to cervical plexus

○ Superior cervical cardiac nerve to heart

Middle Cervical Ganglion (C6) – smallest cervical ganglion; anterior or superior to inferior thyroid artery

Postsynaptic Fibers?????????

○ Gray rami to C5-C6 spinal nerves to brachial plexus?

○ Forms periarterial plexuses to thyroid gland

○ Middle cervical cardiac nerve to heart

Inferior Cervical Ganglion (C7) – usually fused with T1 ganglion to form stellate (cervicothoracic)

ganglion

Postsynaptic Fibers????????

○ Gray rami to C7-T1 spinal nerves to brachial plexus

○ Inferior cervical cardiac nerve to deep cardiac plexus

○ Forms plexus on vertebral artery to cranial cavity

Horner Syndrome – caused by lesion to cervical sympathetic trunk

Causes pupilary constriction, drooping of eyelid, sinking in of eye, vasodilation and absence of sweating on

face and neck

Clinical Case

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Root of the Neck ○ Objectives

Lymphatics of the head and neck: define the major groups of lymph nodes found in the neck. How is lymph returned to the venous

system in the root of the neck?

Root of the Neck

Describe the thyrocervical trunk

Describe the anatomical relationship between the subclavian vessels, brachial plexus, and scalene muscles

Describe the root of the neck, including its boundaries, contents and important anatomical relationships

Describe the relationship between the scalene muscles (especially anterior and middle) and the major vessels and nerves in the

root of the neck

Describe the branches of the subclavian artery

What is the relationship between the subclavian vein, the clavicle, and the first rib

○ Root of Neck

Boundaries

Lateral – Rib 1

Anterior – manubrium

Posterior – T1 vertebral body

Anterior → Posterior

Clavicle → subclavian vein → anterior scalene (with phrenic) → subclavian artery → brachial plexus →

middle scalene muscle

○ Branches of Subclavian Artery

First Part – medial to anterior scalene

Vertebral Artery – goes through transverse foramen of vertebrae

C6-C1 (not C7)

Internal Thoracic Artery – comes out on posterior side

Thyrocervical Trunk ○ Inferior Thyroid – largest; goes up and medial

Ascending Cervical – supplies vertebral column and spinal

cord and travels anterior to TVP

○ Superficial or Transverse Cervical Artery –

Called the Superficial Cervical Artery – if dorsal scapular

artery comes directly off subclavian

Called the Transverse Cervical Artery – if dorsal scapular

artery comes off this branch of the thyrocervical trunk

○ Then this branch will bifurcate into a

Superficial Branch that does the same thing as the superficial cervical artery

Deep Branch – which is the same as the Dorsal Scapular

○ Suprascapular Artery – usually the lowest branch

can arise from subclavian directly

meets up with suprascapular nerve and goes in suprascapular notch on scapula

Second Part – posterior to anterior scalene

Costocervical Trunk – comes off subclavian posteriorly and splits in two

○ Supreme (superior) Intercostal Artery – travels inferiorly to ribs

○ Deep Cervical – travels superiorly, dorsal to TVP

Third Part – lateral to anterior scalene

Dorsal Scapular Artery – can arise from two places

○ 75% - off 2nd

or 3rd

part of subclavian

This means there will be a superficial cervical artery

Dorsal scapular will go through the brachial plexus if it comes directly off subclavian

○ 25% - off of transverse cervical artery

○ Either way, it will meet up and travel with dorsal scapular nerve

○ Either way, it will supply rhomboids and levator scapulae

○ Nerves in the Root of the Neck

Phrenic Nerve (C3-5)

Descends on anterior surface of anterior scalene

Suprascapular and superficial/transverse cervical artery travel over it

Travels between subclavian vein (which is anterior) and subclavian artery (which is posterior)

Vagus Nerve

In carotid sheath, posterior to IJV and CCA/ICA

Right Vagus ○ Enters thorax by passing anterior to 1

st part of subclavian artery and posterior to venous angle (juncture

of brachiocephalic and subclavian vein)

○ Right Recurrent Laryngeal – loops inferior to right subclavian

Left Vagus ○ Enters thorax by passing between CCA and left subclavian artery and posterior to venous angle

(juncture of brachiocephalic and subclavian vein)

Note – recurrent laryngeal nerves ascend to larynx in the tracheoesophageal groove

○ Thyroid and Parathyroid Glands

Thyroid

Goes from C6-T1

2 Lateral Lobes, 1 Isthmus, maybe a Pyramidal Lobe

Surrounded by fibrous capsule

Innervation, arteries and veins are same for thyroid and parathyroid glands

Note – parathyroid glands are on posterior side of thyroid and there can be 2-3 pairs of them

Innervation – sympathetic innervation to arteries

Vasomotor

Arteries

Superior Thyroid – comes off ECA

Inferior Thyroid – comes from thyrocervical trunk

Thyroid Ima – only in 10% of cases

Veins

Superior Thyroid – to IJV

Middle Thyroid – to IJV

Inferior Thyroid – to brachiocephalic; only one of them, usually goes to left

○ Lymphatic Drainage in the Neck

Flow of lymph – superficial cervical nodes → deep cervical nodes → supraclavicular lymph nodes

(accompany transverse cervical artery) → jugular lymphatic trunks

Superficial Cervical Nodes – located along EJV

Deep Cervical Nodes – located along IJV, usually on the carotid sheath

Jugulo-omohyoid Node – right next to intermediate tendon of omohyoid on IJV

Jugulodigastric Node – right next to posterior digastric on IJV

Jugular Lymphatic Trunks – formed by efferent lymph vessels from deep nodes

Left Jugular Trunk – joins thoracic duct

Right Jugular Trunk – joins venous system at

right venous angle

– know all the trunks in picture

○ Cross Section of Neck

See picture above

Note – phrenic nerve, sympathetic chain (in

prevertebral fascia), brachial plexus

○ Clinical Case

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Skull and Cranial Vault ○ Objectives

Identify the major bony landmarks visible from the anterior, lateral, and superior views of the skull

Identify certain areas of the skull that are more vulnerable to injury than others

Identify the sutures and their location. Understand the importance and relevance of these sutures in the adult and newborn skull Describe the relationship of vessels, nerves, and soft tissues as they relate to the bony skull and its foramina and fissures

Identify the essential parts of the anterior, middle and posterior cranial fossae

Describe the composition of the bones of the calvaria

What are diploic veins? What is their clinical significance?

Define the cranial meninges. Describe the relationship of the meninges to the internal surface of the skull. Describe the formation

of a dural fold.

What is a dural sinus? How are they named? Describe how they usually drain. What is the primary blood supply to the cranial dura

○ Skull

22 total bones

Neurocranium (Cranium) – „brain case‟, made of 8 large, flat, curved bones

Viscerocranium (Facial Skeleton) – made of 14 bones

Calvaria – „skull cap‟, made of frontal, parietal, temporal and occipital bones

Cranial Vault – what you see after the calvaria is removed and you look inferiorly

Vertex – most superior point of the skull; occurs between the two parietal bones

Note – the cranium stays pretty much the same size throughout life, it is the facial bones that grow

Anterior View

Frontal Bone – not paired; helps make root of orbit

○ Glabella – the space between the eyebrows

Glabella Reflex – tap a finger on glabella and person will consistently blink if they have dementia

○ Nasion – junction of nasal bones and the frontal bone

○ Superciliary Arch/Ridge – ridge just deep to eyebrows

○ Supra-orbital Margin – sharp edge of frontal bone going down into orbit

○ Supra-orbital Foramen – transmits supraorbital nerve, artery and vein

Maxilla –

○ Body – main part of it

○ Infra-orbital Margin – sharp edge going down into orbit

○ Infra-orbital Foramen – transmits infraorbital nerve, artery and vein

○ Alveolar Process – forms sockets for teeth

Zygomatic Bone – cheek bones

○ Temporal Process – can maybe be seen anteriorly; it is the part that extends to meet temporal bone

Nasal Bone – the bridge of the nose

Mandible – not paired

○ Body – main part

○ Mental Foramen – transmits mental nerve, artery and vein

○ Alveolar Process – forms sockets for teeth

Lateral View

Parietal Bone – the big ones on side

○ Inferior and Superior Temporal Lines – muscles attach here

Temporal Bone – has many features

○ Squamous Portion – flat portion of the bone

○ Petrous Portion – goes into skull

Internal Auditory Meatus transmits CN 7 & 8

○ Mastoid Portion – posterior to external auditory meatus

○ Tympanic Portion – contains the External Auditory Meatus

○ Styloid Process – inferior to external auditory meatus; has 3 muscles connected to it

○ Zygomatic Process – portion that goes anterior to meet the zygomatic bone

Sphenoid Bone – just the greater wing here; between temporal and frontal bones

Occipital Bone – back part

Pterion – the part where the frontal, sphenoid, temporal and parietal bones meet

○ Bones are really thin here and the middle meningeal artery and vein run deep to it and so it vulnerable

to injury

Posterior View

Sutures – immovable joints of the skull

○ Saggital Suture – runs between the 2 parietal bones

○ Coronal Suture – runs between frontal and 2 parietal bones

○ Lambdoid Suture – runs between 2 parietal and occipital bones

Bregma – intersection of the saggital and coronal sutures

○ Was the anterior fontanelle at birth

Lambda – intersection of saggital and lambdoid sutures

○ Was the posterior fontanelle at birth

Note – fontanelles are membranous and usually close before year 1

Cranial Vault

Anterior Cranial Fossa – formed by frontal, ethmoid, and sphenoid

bones

○ Crista Galli – anterior attachment of falx cerebri (a dural fold); at

midline

○ Cribriform Plate – part of ethmoid bone that has lots of little

openings that transmit CN I; at midline

Middle Cranial Fossa – formed by sphenoid and temporal bones

○ Cranial Nerve Openings – 5 of them in sphenoid bone

○ Hypophysial Fossa – depression of sphenoid bone that houses pituitary; part of Sella Turcica

Posterior Cranial Fossa – formed by occipital bone

○ Is the deepest and largest

○ Supports the cerebellum, pons and medulla

○ Foramen Magnum – transmits the spinal cord

○ Jugular Foramen – where the internal jugular vein begins

Transmits CN 9, 10, 11

Calvaria – has interesting bone structure

Has an inner and outer layer of compact bone with a layer of diploe in between

○ Diploe – spongy bone layer of calvaria (makes it lighter)

○ Diploic Veins – run through diploe and drain into dural venous sinuses and thus the meninges

Are valveless and go through the meninges

Diploic tributaries drain into 4 diploic veins (with characteristic names)

○ Cranial Meninges and Such

Continuous with meninges of spinal cord

Pia Mater – not innervated; follows every contour of the brain

Subarachnoid Space – contains CSF

Arachnoid Mater – not innervated

Dura Mater – highly innervated; has two layers (unlike spinal dura mater) that are usually fused, except when

they make a dural sinus

Meningeal Layer – in contact with the arachnoid mater

Endocranium (periosteal layer) – outer layer; fixed to bones; creates the periosteum of the bones

Dural Folds – areas where the meningeal dura separates from the

periosteal dura and forms reflections

These help provide support for the brain

Falx Cerebri – divides brain into right and left hemispheres

○ Largest; suspended from superior aspect of the cranial cavity

Falx Cerebelli – divides the cerebellum into hemispheres

○ Smaller; in posterior cranial fossa

Tentorium Cerebelli – separates cerebrum from cerebellum

○ Perpendicular to falx cerebri (thus goes lateral to medial

Diaphragma Sellae – circular fold that covers pituitary fossa

Dural Sinuses – when meningeal dura starts to form a reflection

then it creates a space between it and the periosteal dura

Lined with endothelium (so it is kinda like a blood vessel)

All drain into internal jugular vein

Veins of brain can drain into these

Superior Saggital Sinus – unpaired; in superior margin of falx

cerebri

Inferior Saggital Sinus – unpaired; in inferior margin of falx

cerebri

Straight Sinus – unpaired; in tentorium cerebelli

○ Runs from inferior saggital sinus to the confluence of sinuses

Transverse Sinus – paired; in tentorium cerebelli along posterior

attachment to occipital bone

○ Connects confluence of sinuses to sigmoid sinus

Sigmoid Sinus – paired; a continuation of the transverse

○ Ends as the internal jugular vein

Cavernous Sinus – paired; adjacent to the pituitary

○ Lots of things can drain here (I don‟t know what) and then they

drain into sigmoid sinus via the petrosal

Superior and Inferior Petrosal Sinus - paired; along superior and inferior margins of the petrous portion

of the temporal bone

○ Connects cavernous sinus to the sigmoid sinus (blood runs anterior to posterior)

Confluence of Sinuses – unpaired; where the superior saggital, straight and occipital sinuses meeth and the

transverse sinuses leave from

Blood Supply to Meninges

Middle Meningeal Artery – primary arterial blood supply to the dura mater; branch of maxillary artery

○ Foramen Spinosum – entry point into the cranium

○ Source – ECA

○ Location – runs in what would be the „epidural space‟, but there isn‟t one and so it becomes embedded

in the bone

○ Clinical Correlation

Pterion (the thin spot of skull) lies right above a part of the middle meningeal artery and thus if you

break the skull at the pterion it could cause a huge bleed

Epidural Hematoma – because it is epidural blood leaks in very slowly and pushes the dura away

from the bone (compressing brain)

○ Symptoms occur many hours after the injury

Intro to Cranial Nerves ○ Objectives

Review the definition and characteristics of a cranial nerve Review the components of a spinal nerve; describe the components of cranial nerves

Name the 12 cranial nerves

For each cranial nerve, identify functional components and relative position in the cranial vault

Name and describe ganglia that are associated with the cranial nerves

Be able to differentiate between sensory ganglia and autonomic ganglia

○ Cranial Nerves

12 Pair

Skeletal muscle and viscera of head and neck

Skin of face and scalp

Named foramina

Mixed, motor only, sensory only

May contain parasympathetics only

31 Pair

Skeletal muscle and viscera of trunk and limbs

Skin of trunk and limbs

Intervetebral foramina

All mixed nerves

I – Olfactory

II – Optic

III – Oculomotor

IV – Trochlear – comes out dorsally

V – Trigeminal

VI – Abducens

VII – Facial

VIII – Vestibulocochlear

IX – Glossopharyngeal

X – Vagus

XI – Accessory kinda comes out below XII

XII – Hypoglossal kinda comes out above XI

Functional Components for Cranial Nerves

Possible Efferent Components

○ General Somatic Efferents (GSE) – supply muscles of the head, neck, body wall and extremities that

arise from myotomes associated with embryonic somites

○ Special Visceral Efferents (SVE) – supply muscles of head, neck, body wall and extremities that aris

from pharyngeal arches

This is a terribly non-discriptive and misleading name

○ General Visceral Efferent (GVE) – supply smooth muscle, cardiac muscle and glands

Note – just parasympathetic fibers for cranial nerves

Possible Afferent Components

○ General Somatic Afferents (GSA) – pain, touch temperature, proprioception from skin, head, neck and

body

○ General Visceral Afferents (GVA) – convey sensory information from viscera

○ Special Somatic Afferents (SSA) – convey sensory information about the special senses of vision,

hearing or balance

○ Special Visceral Afferents (SVA) – convey sensory information about the special senses of smell and

taste Motor Parasympathetic Sensory

Nerve Skeletal

Muscle

(somatic)

Skeletal Muscle

(pharyngeal)

Smooth Muscle or

Glands

Pain, touch or

temperature

Pain from

organs or

mucous

membranes

Special (smell

and taste)

Special

(vision,

hearing,

balance)

1 – Olfactory Smell

2 – Optic Vision

3 – Oculomotor 5 muscles of

orbit

Pupillary sphincter

Ciliary muscle

4 – Trochlear (SO4) Superior

oblique eye

muscle

5 – Trigeminal

- V1 Ophthalmic Skin of face

(forehead, upper

eyelid, cornea, part

of nasal cavity,

part of nose)

- V2 Maxillary Skin of face

(lower eyelid,

cheek, lateral nose,

upper lip, upper

teeth)

- V3 Mandibular -muscles of

mastication

-anterior belly of

digastric

-myohyoid

-2 tensors

Skin of face

(cheek, chin, lower

lip, tongue, lower

teeth)

6 – Abducens (LR6) Lateral rectus

eye muscle

7 – Facial -muscles of facial

expression

-posterior belly of

digastric

-stylohyoid

1. mucous glands of

nasal cavity & oral

cavity, lacrimal gland

2. submandibular

salivary gland,

sublingual salivary

gland

-ear

-external auditory

meatus

Taste on anterior

2/3 of tongue

8 – Vestibulocochlear -hearing

-balance

9 – Glossopharyngeal Stylopharyngeus Parotid salivary gland -posterior 1/3 of

tongue

-carotid body

-carotid sinus

Taste on posterior

1/3 of tongue

Mucous membrane of pharynx

10 – Vagus -muscle of soft

palate

-pharynx & larynx

-mucous glands of

pharynx and larynx

-thoracic and abdominal

organs

-ear

-external auditory

meatus

-mucous

membrane of

larynx

-from organs

Taste on epiglottis

11 – Accessory SCM

Trapezius

12 – Hypoglossal Intrinsic and

extrinsic

muscles of

the tongue

○ She didn't talk about the foramina

Face, Scalp and Parotid Region ○ Objectives List the layers of the scalp. Give the importance of each layer

Describe the blood supply and innervation to the scalp. What is the clinical significance of the arrangement?

Review on your own the major bones of the face.

Describe the sensory innervation and blood supply to the skin of the face

Explain the clinical significance of the „danger triangle‟ of the face

Describe the organization of the skin of the face, list the major muscles and give their action and innervation

Discuss the consequences of interrupting CN V or VII innervation to the face

Describe the location of the parotid gland

Give the relationships of the parotid gland to the surrounding structures

Describe the nerve and vascular supply to the gland

○ Scalp –

„SCALP‟

Skin –

Connective Tissue – very dense with blood vessels and nerves

○ Density makes it hard to get infected

○ Density makes it hard for blood vessels to close if they get cut, thus there is a lot of bleeding

Aponeurosis – flat tendinous sheet between two heads of the occipitofrontalis muscle

Loose Areolar Tissue – CT that is loose and thus lets above layers move around

○ Note – the three layers above the loose areolar tissue are fused very tightly

Pericranium – the periosteum of the skull

Veins

Emmisary Veins – drain scalp into dural venous sinuses

○ Valveless and thus can bring bad things into the dural sinuses?

Innervation

From Cranial Nerves

○ Supratrochlear Nerve – a branch of V1; more medial and only covers

anterior aspect

○ Supraorbital Nerve – a branch of V1; more lateral and covers much of the

superior aspect

○ Zygomatico-temporal Nerve – a branch of V2 (maxillary)

○ Auriculo-temporal Nerve – a branch of V3 (mandibular)

From Ventral Rami

○ Lesser Occipital Nerve – from C2-C3; basically surrounds ear on posterior

side

From Dorsal Rami

○ Greater Occipital Nerve – from C2; gets most of posterior scalp

Note – no C1 dermatome

Blood Supply

Note – all these arteries have veins with corresponding names

Supratrochlear Artery – with supratrochlear nerve; branch of

ICA

Supraorbital Artery – with supraorbital nerve; branch of ICA

Superficial Temporal Artery – terminal branch of ECA

Posterior Auricular Artery – branch of ECA

Occipital Artery – branch of ECA

○ Face

Skin

Skin of face is connected to underlying bones by loose CT not

deep fascia, thus blood from injury can move subcutaneously quite freely

Skin only directly connected to bone at nose and tip of chin

Very vascular

Bones

Nasal – 2

Maxilla – 2

Mandible – 1

Zygomatic – 2

Lacrimal – 2; makes

portion of lateral nasal

wall; in medial orbit

Vomer – 1; makes the nasal septum

Palatine – 2; head palate?; makes posterior hard palate and posterior lateral

nasal wall

Inferior Nasal Conchae – 2; makes lateral nasal cochea

Ethmoid – 1; makes nasal cavity and paranasal sinuses; superior and middle nasal conchae

Sensory Innervation

“know the basic territories of the 3 divisions, not necessarily the individual subdivisions”

Ophthalmic Nerve Branches

○ Supertrochlear nerve, Supra-orbital

nerve, Lacrimal nerve, Infratrochlear

nerve, External nasal nerve

Maxillary Nerve Branches

○ Infraorbital nerve, Zygomatico-facial

nerve (goes down), Zygomatico-

temporal nerve (goes up)

Mandibular Nerve Branches

○ Mental nerve (through mental

foramen), Buccal nerve, Auriculo-

temporal nerve

Blood Supply

Facial Artery – main artery for face;

branch of ECA

○ Submental Artery – a branch; goes to

chin

○ Inferior and Superior Labial branches – goes to lower and upper lips

○ Angular Artery – the end of the facial artery around side of nose

Superficial Temporal Artery –terminal ranch of ECA

Transverse Facial Artery – branch of superficial temporal artery going horizontal

Supraorbital and Supratrochlear Arteries – branches of ophthalmic artery

Veins

○ Veins of face can drain to two places: the facial vein (mainly goes here) or

the dural sinuses

○ Most tributaries of the facial vein can also drain into the dural sinuses, thus

if facial vein gets blocked then the blood can go into the dural sinuses

○ Danger Zone – infection to side of nose between eye and upper lip can

cause venous drainage to go mainly to the dural sinuses and infect the brain

○ Note – facial vein is valveless

○ Note – facial vein has variable termination, but usually to one of the jugular

veins

○ See picture for ophthalmic vein, infraorbital vein, pterygoid plexus and deep facial vein, all of which can

go either to dural sinuses or the facial vein

Muscles of Face

Embedded in superficial fascia

Attachments – skin & loose connection to bones of face

Innervation – CN VII

Derivation – all from 2nd

pharyngeal arch

Platysma – tenses skin of neck and corners of mouth

Occipitofrontalis 1 – no bony attachment

○ Frontal belly – wrinkle forehead and raise eyebrows

○ Occipital belly – over occipital bone

Orbicularis Oculi 3 – closes eye

Zygomaticus Major 7 – draws ↑ corner of mouth, smile

Zygomaticus Minor 8 -

Orbicularis Oris 10 – purses lips

Levator Labii Superioris 11 –

Levator Labii Superioris Alaque Nasi 9 –

Levator Anguli Oris 12 – deep to above

Depressor Anguli Oris 13 – draws corner of mouth ↓

Depressor Labii Inferioris 14 –

Buccinator 16 – keeps cheek from expanding

Muscular Innervation of Face

Facial Nerve – supplies all muscles, but no skin

○ Enters skull at internal acoustic meatus, gives off nerve to petrosal ganglion, ear and tongue then exits

the skull at the stylomastoid foramen (inferomedial to ear)

○ Once it leaves the skull it makes three branches

Muscles of auricle and occipitalis

Stylohyoid and posterior belly of digastric

Parotid gland – once in parotid gland it breaks into 5 branches

○ “Two Zebras Bit My Cookie” (distributed like your 5 fingers)

○ Temporal Branches –

○ Zygomatic Branches –

○ Buccal Branches –

○ Marginal Mandibular Branches –

○ Cervical Branches –

○ Bell’s Palsy – trauma to facial nerve causes loss of function to muscles of facial expression

Can be temporary

Can‟t close eye and eyes can dry out

Can be caused by middle ear infection, since the facial nerve innervates that and goes right by it

○ Parotid Gland

Largest salivary glands; lies posterior to jaw bone superficially

Parotid Duct – goes over masseter muscle → pierces buccinator muscle → opens adjacent to 2nd

upper molar

Things that traverse or lie deep to the parotid gland

Facial Nerve

External Carotid Artery exits gland as the superficial temporal artery

Retromandibular vein

Auriculo-temporal nerve (branch of V3)

Endocrine 1 – Hypophysis and Pineal ○ Objectives

Describe the histology of the pituitary gland; include the infundibular stalk, the four main parts, and its embryology

Identify chromophils and chromophobes of the pars distalis. Indicate which pituitary hormones are made by each, what are the functions of each hormone and what is the target organ, tissue or cell of each.

Identify the components of the neurohypophysis

Describe the two hormones that are liberated from the posterior lobe of the pituitary in terms of their origin, the hypothalamophyseal

tract, their target organs, and their functions

Be able to describe the signals which trigger the release of pituitary hormones and their feedback regulation

Describe the overall histology of the pineal gland and the hormones produced by the pineal gland

○ Hormones

Sites of Action

Circulating – travel through circulation to act on distant tissues

Paracrine – act on neighboring cells and tissues

Autocrine – act on the same cells that secrete them

Chemical Classes - Steroid Hormones (testosterone, work in days), Protein Hormones (prolactin, work in

minutes), Amino Acid Derivatives (norepinephrine, work in seconds)

Effective at low concentrations; often have feedback control

Direct Action Hormones – often lipid soluble and get into cell membrane or nucleus to modulate something

Indirect Action Hormones – often water soluble and bind to a membrane receptor that activates a membrane-

bound enzyme → which activates a secondary messenger (cAMP) → intracellular signaling cascade

Often used by peptide hormones

○ Endocrine System – ductless glands whose secretions are passed directly to blood or lymph

Ex. pituitary, thyroid, parathyroid, adrenals, pancreatic islets, pineal, testis, ovaries

Embryological Origins

Ectoderm – pituitary, adrenal medulla, pineal, enterochromaffin cells

Mesoderm – adrenal cortex, testis, ovaries

Endoderm – islets of Langerhans, parenchymal cells of thyroid and parathyroid

Structure of Glands

Plates/cords of parenchymal cells separated by sinusoids supported by delicate CT

Highly vascularized with fenestrated capillaries

Types of Tissue

Distinct Aggregates of cells – the endocrine organs (pituitary, thyroid, parathyroid, adrenal, pineal)

Isolated Cells – often in lining of GI or respiratory system (enterochromaffin cells)

Scattered Masses – endocrine tissue in exocrine glands or other organs (leydig cells, corpus luteum,

juxtaglomerular cells of kidney, islets of langerhaans

○ Pituitary Gland

Master gland because it regulates secretions of major hormones

Acts with hypothalamus

Covered by CT capsule, diaphragma sellae

Overview of Lobes

Anterior Lobe (Andenohypophysis)

○ Derived from roof of oral ectoderm

○ Made of pars distalis, pars tuberalis, pars intermedia (vestigial in humans)

○ Blood Supply – from superior hypophyseal arteries, which come from internal carotids

Forms anastomosis around infundibulum and median eminence to create the Primary Plexus which

contains lots of fenestrated capillaries

○ → Hypophyseal portal vein → Secondary Plexus (where the anterior lobe dumps its contents,

made of sinusoidal capillaries) → inferior hypophyseal veins → cavernous sinus

Hypothalamic hypophyseal portal system – primary to secondary plexus

○ Allows regulatory peptides from hypothalamus to get to anterior lobe

○ Some of the stuff secreted – GH, LTH, FSH, LE, TSH, ACTH

Posterior Lobe (Neurohypophysis)

○ Derived from neuroectoderm of hypothalamus

○ Made of pars nervosa, infundibulum, median eminence

○ Blood Supply – from inferior hypophyseal arteries, which come from internal carotids

→ plexus → posterior hypophyseal veins

○ Anterior Lobe in Depth

Pars Diatalis – 75% of pituitary

Dense cords of secretory epithelial cells supported by reticular fibers

Sinusoidal capillaries – lined by endothelial cells that are fenestrated with diaphragms

Chromophobes – small, round pale staining cells with relatively little cytoplasm

○ non-secretory

○ Thought to be degranulated chromophils

○ Tumors are common and destroy surrounding tissue

Chromophils – like stain and are thus darker. Different types secrete different hormones

○ Acidophil Chromophils (α cells) – large, densly staining cells

Lots of acidophilic granules

Somatotrophs – can‟t be distinguished from mammotrophs without antibodies

○ Spherical to ovoid

○ Centrally located nucleus

○ Large secretory granules contain Growth Hormone (Somatotrophin)

Growth Hormone – protein hormone that stimulates chondrocyte growth and cartilage matrix

secretion (in bones)

Pituitary Dwarfism – deficiency in GH during development, long bones don‟t grow

Pituitary Gigantism – overproduction of GH during development prolongs bone growth

Acromegaly – overproduction of GH during adulthood (after closure of epiphyseal plate)

that results in ↑ bone production and overgrowth in the extremities

Regulates release of Somatomedins, which are „insulin-like‟ growth factors made in liver

which stimulate cartilage growth and mitosis

Mammotrophs – can‟t be distinguished from somatotrophs without antibodies

○ Small, irregularly shaped cells concentrated in posterolateral portion of Pars Distalis

○ Smaller granules contain Prolactin

Stimulates and maintains the production/secretion of milk

Maintains corpus luteum to stimulate progesterone secretion

Hyperplasia of mammotrophs and their granules occurs during pregenancy

○ Basophil Chromatophils (β cells) – Larger than acidophils; granules smaller and less numerous

Note – different classes can only be differentiated with antibodies

Thyrotrophs – make thyroid stimulating hormone

○ Usually farther away from sinusoids

○ TSH stimulates thyroxidine and triodothyronine (T4 and T3) from thyroid gland

○ No TSH → thyroid atrophy

○ ↑ TSH → hyperthyroidism

○ ↓ T4 & T3 → removes the feedback mechanism and causes ↑ TSH

Gonadotrophs – fusiform cells; eccentric nucleus; varying sized granules

○ Usually adjacent to sinusoids

○ Follicle Stimulating Hormone

Females – promotes growth of ovarian follicles

Males – promotes spermatogenesis by stimulating androgen binding protein production in

Sertoli cells

○ Leutinizing Hormone

Females – promotes ovulation; stimulates progesterone secretion from corpus leuteum

Males – maintains Leydig cells and stimulates androgen secretion in them

Corticotrophs – ovoid cells with eccentric nucleus

○ Produces pro-opiomalanocortin which is cleaved into:

Adrenocorticotropic Hormone – stimulates release of glucocorticoids from adrenal cortex

β-Endorphin – opiate-like; involved in pain system

Melanocyte Stimulating Hormone – stimulates melanin synthesis in melanocytes

β-Lipoprotein – unknown function

Pars Tuberalis – collar of cells wrapped around the infundibular stalk

Longitudinally organized cords

Vasculature of hypothalamo-hypophyseal portal system goes through this

Contains mostly gonadotrophs

Pars Intermedia – rudimentary, thin layer of chromophobic cells surrounding Rathke’s Cysts (aggregates of

colloid filled follicles)

Between anterior and posterior lobes

Hormonal secretions unclear, maybe some melanocyte stimulating hormone

In lower mammals it is much larger (20%) and contains basophilic cells and Rathke’s Cleft which is an

indentation

Neuroendocrine Link of Anterior Pituitary

Hypothalamic hypophysiotropic peptides – made by basal hypothalamus and are „releasing factors‟ that

modulate release of hormones from the anterior pituitary

○ Made in specific hypothalamic regions by small neurons that have unmyelinated axons that terminate on

fenestrated capillaries of the primary plexus (then travel via portal vein → secondary plexus of anterior

lobe)

There are also a few „release-inhibiting hormones‟

There is a table of related hypothalamic hormones, do we need to know it?

○ Posterior Pituitary in Greater Detail (Neurohypophysis)

Pars Nervosa

Three Elements

○ Dense Capillary Plexus

○ Pituicytes – highly branched, non-secretory, glial like cells, provide nutrients; end on capillaries

○ Tons of unmyelinated axons of neurosecretory cells of the supraoptic and paraventricular region of

hypothalamus

Hypothalamic hypohyseal tract – tract of these axons that terminate near the fenestrated capillaries

of the capillary plexus

Stuff secreted by exocytosis

Neurophysin – carrier protein that carries hormones down the axon

Herring Bodies – visible dilations of axons containing vesicles of hormones

No secretory epithelial cells

Hormones

○ Oxytocin – peptide made in the paraventricular nucleus of the hypothalamus

Induces peristaltic contractions of uterine smooth muscle

Induces contraction of myoepithelial cells of mammary gland resulting in excretion of milk

○ Vasopressin (antidiuretic hormone) – peptide made in supraoptic nucleus of hypothalamus

Promotes water resorption through the collecting tubules of the kidney

↑ BP by promoting contraction of vascular smooth muscle resulting in ↑ peripheral resistance

○ Endocrine Feedback Mechanisms

Negative – output of target cells ↓ hormone production

Positive – output of target cells ↑ hormone production

1st Order Regulation – neurohypophyseal hormone acts on non-endocrine target (ie oxytocin, vasopressin)

levels of product from target in blood feed back to hypothalamus regulating the neurohypophyseal hormone

2nd

Order Regulation – hypothalamic releasing factors stimulate release of anterior pituitary hormones

levels of anterior pituitary hormones in blood feed back to hypothalamus or pituitary

Ex growth hormone, prolactin

3rd

Order Regulation - hypothalamic releasing factors stimulate release of anterior pituitary hormones which

then causes release of another hormone from an endocrine organ

levels of this new hormone in blood feed back to hypothalamus or pituitary

Ex thyroid stimulating hormone, ACTH

○ Pineal Gland

Flattened, conical gland attached to diencephalon of CNS

Encapsulated by pia mater of CNS, which also penetrates parenchyma as trabeculae

Pinealocytes – basophilic cytoplasm with long cytoplasmic processes ending in bulb-like expansion in close

proximity to capillaries, which contain vesicles that are exocytosed into the capillaries

Large oval nucleus and clearly distinguishable nucleoli

Melatonin – synthesized from serotonin

○ Causes pigment retention in melanophors

○ May be free radical scavenger; may inhibit growth and metastasis of some tumors

○ Release is inhibited by light; overproduction may be involved in seasonal affective disorder; involved in

sleep/wake cycle

Glial Cells – resemble astrocytes

Brain Sand – characteristic small aggregates of calcium phosphate and calcium carbonate

○ Are radiopaque and ↑ with brain lesions or compression

Endocrine 2 – Thyroid, Parathyroid, Adrenal Glands ○ Objectives

Describe the histology of the thyroid gland

Describe the function of thyroid follicular cells and the synthesis, storage and secretion of thyroid hormone

Describe and identify the parafollicular (C cells)

Describe and identify the histology of the parathyroid glands. Distinguish the chief (principle) cell from the oxyphil cell

Describe the overall histology of the adrenal gland, its blood supply, and the embryological origin of each region

Describe the three zones of the adrenal cortex, their constituent cells, and substances produced by the cells in each zone Describe the functions of each hormone secreted by the adrenal gland and the clinical disorders associated with each

Describe the organization of the adrenal medulla and it‟s constituent cells

Indicate which cells of the adrenal medulla secrete hormones, and identify the hormones secreted by each

Identify the endocrine component of the pancreas, the specific hormone producing cells and the functions of each hormone

○ Thyroid

Regulates tissue metabolism, tissue growth, and secondary regulation of plasma Ca++

Right, left, ishmus and pyramidal lobes

Embryology

Develops as median downgrowth of the base of the tongue and descends to the upper tracheal region

leaving a duct behind, the thyroglossal duct (obliterated during development)

Enclosed by two layers of CT, an external dense CT layer, and an inner, thin layer that penetrates the lobes

Thin layer of CT divides thyroid into lobules

Follicles – functional and structural subunit of thyroid

Spherical cyst-like structures bounded by follicular epithelial cells

Follicular Epithelial Cells – simple cuboidal epithelial cells that form outer, single-layer border of follicle

○ Synthesize the secretions

Also surrounded by a basal lamina and supported by reticular fibers

Enveloped in meshwork of fenestrated capillaries that receive the endocrine secretion

Colloid – gelatinous substance in center of each follicle

○ Contains stored products of the follicular epithelial cells

Cells of Thyroid

Parafollicular (C-Cells) ○ Less numerous cell; found in walls of thyroid follicles (between and within?)

Within the basement membrane of the follicle, but are insulated from the lumen by cytoplasmic

extensions of the follicular cells

○ Originate from neural crest (from APUD cell line)

○ Larger and lighter staining

○ Centrally located nucleus

○ Vesicles contain calcitonin

○ Calcitonin – peptide that ↓ plasma Ca (in direct response to elevated Ca levels) via

Inhibiting osteoclast activity (which ↓ bone resorption and thus the freeing of Ca)

Promoting excretion of Ca (in kidneys)

Not under control of the pituitary

Follicular Epithelial Cells ○ Structure

Cytoplasm is slightly basophilic; centrally-located nucleus; usually simple cuboidal

If hyperactive → cells become columnar, colloid is ↓, inner border will become “scalloped”

If hypoactive → cells become squamous and colloid ↑ a bunch

EM Level – features of a cell making a lot of exported proteins are displayed

○ Tight junctions at lateral borders

○ Dilated cisternae of RER, colloid droplets, numerous coated vesicles, and

microvilli

○ Function

Synthesize thyroid hormone

Thyroglobulin – precursor to thyroid hormone that is a major component of

the colloid

Note – follicular cells are unique endocrine cells since they store their product

extracellularly

○ Synthesis of Thyroid Hormone

Thyroglobulin made in rER and processed in golgi

Tyrosine residues added to it and shipped in vesicles to surface, where it is

exocytosed

Thyroperoxidase – enzyme that stays right near the microvilli of the follicular

epithelial cells (made by same cells) that catalyzes the iodination of thyroglobulin

○ Note – this reaction occurs in the lumen of the follicle within 1-2 µm of microvilli

Note - Iodide Pump on basal side of membrane brings in iodide from the plasma

○ Iodide is oxidized in the cell and forms iodine which is then secreted into the follicular lumen

Iodinated Thyroglobin formed after iodine is added

○ 1 added – MIT; 2 added – DIT (are just iodine carriers; are deiodinated and recycled in cell)

○ MIT + DIT = T3 (active form of thyroid hormone)

○ DIT + DIT = T4/thyroxine (active form of thyroid hormone)

Iodinated thyroglobin is taken up by apical surface and formed into colloid droplets

○ It is then digested by lysosyme and T3, T4, MIT and DIT are made

T3 and T4 then diffuse out basal membrane surface and into capillary circulation where they are

bound by plasma proteins

○ Regulation of Thyroid Hormone

Activated by thyroid stimulating hormone released by the anterior pituitary

○ Causes hypertrophy and hyperplasia of follicular cells

○ ↑ production and iodination of thyroglobulin

○ ↑ re-uptake and lysosomal digestion of iodinated thyroglobulin

○ ↑ secretion of T3 and T4

Plasma levels of T3/T4 are monitored by the hypothalamus

If too low then

○ TSHreleasing hormone released into hypothalamic portal system and stimulates TSH release from

anterior pituitary thyrotrophs

○ Follicular cells in thyroid respond and release more T3/T4

○ Increased levels in blood stop TSHrh release in hypothalamus

○ Function of Thyroid Hormone

Metabolic Effects

○ Controls Basal Metabolic Rate (kilocalories/square meter of body surface/hour) energy

expenditure at rest

○ Regulates water and ion transport

○ Reulates protein, fat and carbohydrate metabolism

Growth Promoting Effects

○ Acts synergistically with growth hormone to promote skeletal development

○ Controls molting and metamorphosis in lower vertebrates

○ Thyroid Dysfunction

Hypothyroid Hyperthyroid

Mentally and physically sluggish Restless, irritable, anxious

Low BMR Elevated BMR

Mental retardation Mentally alert

↓ glucose absorption ↑ glucose absorption

Weak heartbeat Tachycardia

Hypothyroidism

○ If during development → Cretinism – stunted physical and mental growth with big belly

○ If during adulthood → Myxedema – lethargy and mental deficiencty

○ Hashimoto’s Disease – autoimmune destruction of follicular cells

Goiter – enlargement of thyroid gland due to hypertrophy and hyperplasia of follicular cells

○ Can be caused by:

Iodine Deficiency – causes ↓ T3/T4 output → ↑TSH release → follicular hypertrophy

Graves Disease – thyroid stimulating immunoglobulin causes stimulation of follicular cells

Also causes protrusion of eyeballs due to increased water absorption in retro-occular tissues

○ Importance of Calcium

Most abundant cation

Membrane permeability, excitability of muscles and nerves, enzyme activity, blood clotting, acid/base

Absorbed by SI but Vit D is required

Minor fluctuations in plasma concentrations can have large effect

Hypercalcemia – ectopic calcification of soft tissues; kidney stones

Hypocalcemia – hyperexcitability of neurons; prolonged skeletal muscle contractions; aberrant cardiac

muscle contraction

○ Parathyroid Glands

Maintain appropriate plasma concentrations of Ca

4 small glandular masses on posterior thyroid (in pairs)

2 inferior parathyroids derived from 3rd

pharyngeal arch and descend with the thymus

2 superior parathyroids derived from 4th

pharyngeal arch and descend with the thyroid

Lie just outside of thyroid capsule, but enclosed in same fascia

CT septa carry blood into tissue, but don’t separate it into lobes

Cells arranged in cords supported by reticular fibers and separated by fenestrated capillaries

Types of Cells

Chief Cells ○ Structure – most numerous cell; small; centrally located nucleus

If cytoplasm is light → Light Cells – inactive

If cytoplasm is dark → Dark Cells – active and secreting parathyroid hormone

EM Level

○ Irregularly shaped secretory granules, but they are less numerous than in other endocrine glands

because the parathyroid doesn‟t store much PTH

○ Function – secretes parathyroid hormone (PTH)

Three Effects when blood Ca is ↓ (thus not under control of pituitary)

○ ↑ release of osteoclast stimulating factor which stimulates osteoclast activity to ↑ bone

resorptoin and thus ↑ Ca release

○ ↑ Ca resorption – by distal convoluted tubules

○ Promotes synthesis of dihydroxycholecalciferol (a Vit D derivative) to ↑ Ca absorption in SI

Oxyphil Cells – unknown function

○ Less numerous; larger (more cytoplasm), dark staining nuclei, strongly acidophilic cytoplasm

○ EM Level – there is a ton of mitochondria

○ Don‟t appear until age 7

○ Pancreatic Islets of Langerhans

Structure

Endocrine „micro-organs‟/clusters of cells in pancreas

More concentrated in tail region of pancreas

Encapsulated by reticular fibers

Cells are pale and a little smaller than surrounding acini of pancreas

Function

Stimulate digestion

Regulates glucose transfer

Types of Cells

Alpha Cells – secretes Glucagon which ↑ blood glucose by breaking down glycogen

○ 20%; large cells; in periphery of islet; numerous granules

○ EM – eccentrically place electron dense core

Beta Cells – secretes Insulin which ↓ blood glucose by 1. promoting glucose transfer into tissue and 2.

stimulating formation of glycogen

○ 70%; small cells; center of islet

○ EM – electron dense core

○ Diabetes Mellitus – hyperglycemia, glucosuria, polyuria (increased excretion of water)

Type 1 – reduced beta cell secretion

Type 2 – defect of insulin receptors on tissue cells

Delta Cells – secrete Somatostatin and in the pancreas it affects glucagon and insulin release

○ Somatostatin can be a neurotransmitter or a neurohormone

When released by hypothalamus it causes growth hormone release

When released in pancreas it affects glucagon and insulin release

F Cells – secretes pancreatic polypeptide which:

○ Stimulates release of gastric secretions in gut

○ Inhibits bile secretion in the gall bladder

G Cells – secrete Gastrin which 1. increase HCl secretion in stomach 2. ↑ gastric motility

○ Only present during maturation

Note

○ α, β and D cells are connected by gap junctions and thus secretions influenced by local diffusion

(paracrine)

○ Glucagon and insulin levels are changed in response to increased or decreased plasma glucose levels

○ Adrenal Glands

Covered by thick fibroelastic CT capsule with rich blood supply

Cortex and medulla can be considered 2 separate endocrine tissues because they have different:

Embryological origin; hormonal secretion; function

Blood Supply – superior (from inferior phrenic), middle (from aorta), inferior (from renal artery)

Capsular Arteries – continuation of above arteries in the capsule, where they branch to form:

○ Cortical Arterioles – branch a bunch immediately and create

Capillary plexus of cortex and cortical sinusoids

○ Medullary Arterioles – go deep and create capillary plexus of the medulla

○ Note – the capillaries create are fenestrated sinusoid (just like other endocrine organs)

Cortex

Function

○ Secretes different Steroid Hormones

Mineralcorticoids – affect fluid and electrolyte balances by promoting resorption of Na from 1. the

distal convoluted tubules and 2. the sweat and salivary glands

○ Secretion controlled primarily by renin/angiotensin system but also stress related ACTH

○ Aldosterone and deoxycorticosterone

Glucocorticoids – cortisol, cortisone, corticosterone

○ Downregulate the immune system – inhibit lymphocyte production

○ Modulation of carbohydrate metabolism – promotes formation of glucose from protein

○ Suppression of inflammatory response - ↓ production of T-cells and plasma cells

○ Negative feedback control over release

Hypothalamic neurosecretory cells release corticotrophin releasing factor

Corticotrophs in anterior pituitary release ACTH

When glucocorticoid levels are too high, then levels of this stuff decreases??????

Gonadal Steroids – effects are similar to hormones secreted by test?is

Secretion controlled by ACTH of anterior pituitary and the renin/angiotensin system

Structure

○ Made of secretory epithelium supported by reticular fibers

○ Encapsulated by fibroelastic CT which penetrates and brings nerves and BV

○ Layers (distinction between the layers is gradual)

Zona Glomerulosa – 15%; thin outer layer

○ Small columnar cells arranged in spherical aggregates surrounded by capillaries

○ Dark staining nuclei

○ EM Level – numerous mitochondria with lamellar cristae

○ Function – release 2 mineralcorticoids: Aldosterone and Deoxycorticosterone

Zona Fasciculata – 78%; thick middle layer

○ Long, radially oriented cords of secretory epithelial cells separated by capillaries

○ Larger cells; centrally located nuclei, sometimes binucleated

○ Cytoplasm contains numerous lipid droplets

○ Membrane near capillaries will have short microvilli extending into it

○ Numerous mitochondria

○ Function – secretes glucocorticoids: Cortisol

Zona Reticularis – 7%; thin inner layer

○ Irregularly anastomosing cords separated by sinusoids

○ Numerous secondary lysosomes and lipofuscin pigment granules

○ Function

Secretes a little cortisol

Secretes several weak steroidal androgens that aren‟t stored, but synthesized and released

Secretions here aren‟t significant unless there is a tumor (which causes ↑ release)

Male tumor – early development of sex organs and secondary sex characteristics

Female tumor - Adrenogenital Syndrome causing androgenization of genitalia,

development of male secondary sex characteristics and if present in womb then can cause

pseudohermaphroditism

○ Dysfunction

Addison’s Disease – hypoadrenalism due to idiopathic atrophy of cortex

○ Fatigue, weakness and drowsiness – due to low blood glucose (↓ glucocorticoids)

○ ↓ BP & ↓ adsorption of Na – due to ↓ mineralcorticoids

○ ↑ ACTH secretion

○ Darkening of the skin

Cushings Disease – hyperadrenalism can be caused by tumors or excessive synthetic glucocorticoid

use

○ Moon face – redistribution of fat around neck, face and abdomen

○ Muscle wasting – due to antianabolic effects of glucocorticoids (tissue of limb muscle and bones

broken down)

○ Thinning of skin – loss of fat in hypodermis (blood vessels can show through)

○ Hyperglycemia

Medulla

Composed of chromaffin cells arranged in irregular cords between wide

fenestrated capillaries and supported by reticular fibers

Chromaffin Cells ○ Large, ovoid, pale cells

○ EM – dense core granules containing catecholamines

○ Derived from sympathetic ganglion cells of the celiac plexus that migrated in

○ Neurons that have lost their axonal and dendritic processes and are just

secretory

○ Innervated by preganglionic sympathetic fibers with cholinergic synapses

○ Types – distinguished by immunocytochemistry or EM

Epinephrine Cells – 80%; have round granules in the vesicles

○ Cluster around adrenal sinusoids

Norepinephrine Cells – 20%; have flattened or ovoid granules with dense core, but su?rrounded by

less dens?e ring (it seems that epinephrine granules have this too??)

○ Granules are darker

○ Cluster around adrenal arterioles

Are the descriptions for the granules really right?

Reasoning for different distribution

○ Epinephrine is synthesized from norepinephrine and the enzyme that does this is glucocorticoid-

induced

Thus, epinephrine cells are closest to adrenal sinudoids so that they can receive the

glucocorticoids and norepinephrine cells are farther away and don‟t receive the glucocorticoid

○ Catecholamine Function

Released from medulla due to impulses of the sympathetic preganglionic fibers

Reinforce actions of sympathetic nervous system in preparation for stress

○ Elevate blood glucose

○ ↑ BP and CO

○ Dilate coronary and skeletal muscle blood vessels

○ Cutaneous vasoconstriction

Temporal and Infratemporal Fossae ○ Objectives

Define the temporal fossa

What are the contents of the temporal fossa?

How do you define the infratemporal fossa? Do the temporal and infratemporal fossae communicate?

What are the contents of the infratemporal fossae?

What foramina are associated with the infratemporal fossa?

What are the muscles of the fossa?

What are the major blood vessels of the fossa?

What are the nerves of the fossa?

What is the otic ganglion? Where is it located? What is its significance? Are there any other ganglia in the infratemporal fossa?

What is the chorda tympani? How did it acquire its name? How is it associated with the infratemporal fossa?

Can you differentiate between sensory and motor nerves as they relate to the infratemporal region?

○ Mandible

External Structures

Body – the horizontal part

Ramus – the vertical part

Angle – where the body and ramus meet

Head/Condylar Process – posterior point; where mandible articulates with temporal bone (TMJ)

Mandibular Notch – scooped out portion; masseteric N, A & V go through here

Coronoid Process – anterior point; where temporalis muscle attaches

Mental Foramen – transmits mental N, A & V

Internal Structures

Lingula – where sphenomandibular ligament attaches; it is a little spike; on ramus

Mandibular Foramen – entrance to mandibular canal which exits at the mental foramen; houses nerve

for teeth

Mylohyoid Groove – made by nerve to mylohyoid, which branches off of the inferior alveolar nerve

Mylohyoid Line – point of attachment for the mylohyoid; runs along inside body

Mental Spine – below front teeth; attachment of geniohyoid and genioglossus muscles

Mandible and Age

With age your facial skeleton will normally shrink a little

If you loose your teeth then the bone sockets will fill in

○ The mandible will shrink significantly if you loose your teeth; it can shrink so much that it opens the

mental foramen

○ This is why dentures constantly need to be refitted

○ Sphenoid Bone

Lesser Wing –

Superior Orbital Fissure – kinda right in between greater and lesser wings

Greater Wing –

Foramen Rotundum – transmits V2

Foramen Ovale – transmits V3

Foramen Spinosum – transmits middle meningeal artery

Body – stuff in the middle that isn‟t one of the wings

Sella Turcica – where pineal gland lays

Inferior Surface

Lateral Pterygoid Plate – where some muscles of mastication attach; at more of an angle

Medial Pterygoid Plate – where some muscles of the soft palate attach

○ Temporal and Infratemporal Regions

Zygomatic Arch – boundary between the two regions

Made by temporal process of zygomatic bone and zygomatic process of temporal bone

Temporal Fossa – runs deep to zygomatic arch; filled by temporalis muscle

○ Connects the temporal and infratemporal regions

Temporal Region – bounded by temporal lines, frontal and zygomatic bones

Infratemporal Region

Boundaries

○ Anterior – maxilla

○ Superior – greater wing of sphenoid

○ Medial – pterygoid plate of sphenoid

○ Lateral – ramus of mandible

○ Posterior – tympanic portion of temporal bone

Contents

○ Portions of muscles of mastication

○ Branches of the maxillary artery

○ Pterygoid plexus of veins

○ Branches of the mandibular nerve (V3)

Muscles

○ Actions

Protraction – push jaw anteriorly

Retraction – bring jaw posteriorly

Elevation – biting

Depression – actually not an action of muscles of mastication, done by suprahyoid muscles

Note – grinding teeth is done by alternate protraction (right) and retraction (left)

Origin Insertion Action Nerve

Temporalis -inferior temporal line

-temporalis fascia (which attaches to superior temporal line)

-coronoid process to anterior aspect of ramus -Elevation

-Retraction V3

Masseter (main

chewing muscle)

-zygomatic arch

-zygomatic bone

External aspect of ramus -Elevation

-Protraction

Medial Pterygoid (fibers in same

orientation as masseter)

-medial surface of lateral

pterygoid plate

-posterior maxilla (this head goes

over lateral pterygoid muscle)

Internal aspect of ramus (inferior to

mandibular foramen)

-Elevation

-Protraction

Lateral Pterygoid (runs horizontally)

-lateral surface of lateral

pterygoid plate

-sphenoid bone

-mandibular head

-articular disc of TMJ

-Protraction

(strongest)

Blood Supply

○ Maxillary Artery A terminal branch of the ECA

Posterior to ramus

Can lie anterior or posterior to the

lateral pterygoid muscle

○ If maxillary artery is deep to muscle

then temporal and middle meningeal

arteries kind of switch places (thus

make sure you identify arteries by where they go)

2/3rds of it stays in infratemporal fossa (supplies most muscles of mastication) and last 1/3rd

goes to

the posterior aspect of the nasal cavity (pterygopalatine fossa)

Branches

○ Middle Meningeal – goes through foramen spinosum into skull and out middle cranial fossa to

supply dura mater

Frequently encircled by the auriculotemporal nerve

○ Accessory Meningeal – if present, then it goes through foramen ovale and supplies dura mater

○ Inferior Alveolar – enters mandibular canal, gives dental branches to teeth, exits bone through

mental foramen and becomes mental artery

○ Deep Temporals – stay superficial and end in temporalis muscle

○ Posterior Superior Alveolar – pierces maxilla and supplies posterior upper teeth

○ Inferior ophthalmic artery and sphenopalatine artery at end

○ Pterygoid Plexus of Veins

Lies deep to the temporalis muscle but above the pterygoid muscles

Receives veins from – superficial face (facial vein), orbit (ophthalmic

vein), and pharynx

Drains into – either the jugular system or the cavernous sinus (thus the

dural venous sinuses)

Nerves

○ Mandibular Nerve

Motor Branches - all of these muscles are derived from the 1st pharyngeal

arch

○ To muscles of mastication – temporalis, masseter, medial and lateral

pterygoid

○ To tensor muscles – tensor tympani (in middle ear, dampens sound), tensor veli palatini (muscle

of soft palate)

○ Nerve to Mylohyoid – supplies

mylohyoid

○ Branch to anterior belly of digastric -

Sensory Branches – find these in lab

○ Auriculotemporal Supplies skin of anterior ear, temple,

lateral scalp

Often divides to let middle meningeal

artery through

Travels onto skin with superficial

temporal artery

○ Inferior Alveolar

Gums and teeth of lower jaw

Enters mandibular canal, branches to

teeth, goes out of jaw through mental

foramen to become the mental nerve (which supplies lower lip and chin)

Branch separates and supplies the mylohyoid (branch leaves before going into the jaw)

○ Lingual Supplies anterior 2/3 of tounge (pain, touch and temp)

Supplies gums and mucous membrane in the floor of the oral cavity

○ Buccal

Supplies skin of cheek (outside) and

Pierces buccinator and supplies mucous membrane on inside of cheek

Otic Ganglion – parasympathetic ganglion of CN 9 that helps innervate parotid gland

○ Preganglionics – split off of CN 9 to form lesser petrosal nerve which goes through the foramen ovale

with V3 and end in the otic ganglion

○ Postganglionics – travel along auriculotemporal nerve (which splits around middle meningeal artery)

and hop off at parotid gland

Chorda Tympani – a branch of the facial nerve (CN 7) that joins (becomes intertwined with) the lingual

nerve (a branch of V3) in the infratemporal fossa

○ Carries taste fibers from the anterior 2/3rds of the tongue

○ Carries preganglionic parasympathetic fibers to the submandibular ganglion and thus the

submandibular and sublingual glands

○ Note – know your lesions to the lingual, facial, and chorda tympanii nerves

Orbit ○ Objectives

Identify the orbit and its constituent parts

Discuss the importance of the position of the orbit in the skull

Identify the components of the eyelid. Describe how each component contributes to the function of the eyelid

Describe the location of the lacrimal gland, its innervation and blood supply, and the structures involved in moving tears across the

eye

Identify the extraocular muscles and the innervation of each. Understand the following features of extraocular movements

Primary action of extraocular muscles with eyes in primary gaze

How to test each extraocular muscle, including what position the eye should be in to isolate the primary action of each muscle

Which muscles work together („cross pairs‟ rule) to elevate/depress the eyes (e.g. when you ask a patient to „look up‟ from

primary gaze)

What happens to the direction of gaze of an eye in which innervation to one or more extraocular muscles are interrupted

Identify the nerves of the orbit. What is Horner‟s syndrome?

Identify the vasculature of the orbit. What is the significance of the cavernous sinus with regard to nerves that supply structures in

the orbit?

○ Surface features of the Eye and Orbit

Palpebral Fissure – space/opening between eyelids

Medial Canthus – medial angle where upper and lower lids unite

Lateral Canthus – lateral angle where upper and lower lids unite

Lacrimal Caruncle – fleshy, yellowish mass in the medial canthus that contains modified sweat and oil

(sebaceous) glands

○ Bones

Roof – Frontal bone (also some lesser wing of the sphenoid)

Floor – Maxilla (also zygomatic and palatine)

Medial – Ethmoid (frontal, lacrimal & sphenoid)

Medial walls are parallel to each other

Lateral – Zygomatic (greater wing of sphenoid)

Lateral walls are at 90º to each other

Orbital Axis – at a 23º angle from the axis of the eyeball (which

is straight on)

Note – orbit has a pyramid shape

○ Orbital Blowout Fracture

Fracture to the bones of the orbit, usually the floor (since it is the

thinnest)

Due to blunt object causing increase in pressure in the orbit and causes tissue to fly through bone

Inferior rectus is often the muscle to fly out of the orbit

Symptoms - Eccymosis („black eye‟), diplopia with upward gaze due to entrapment of inferior rectus, facial

anesthesia (due to infraorbital nerve damage), nose bleed, sinking in of eye, bleeding into sinuses

○ Openings

Optic Canal – lets CN II and ophthalmic artery through

Superior Orbital Fissure – between the greater and lesser wing of the sphenoid

Common Tendinous Ring – surrounds the optic canal and part of the superior orbital fissure

○ Common origin for the four recti muscles

○ Inside Ring – through superior orbital fissure - CN 3,

CN 6, nasociliary nerve (off V1),

Inside ring associated with optic canal - CN II,

ophthalmic artery

○ Outside Ring – Frontal and lacrimal nerves (off V1),

CN 4, superior and inferior ophthalmic veins

Inferior Orbital Fissure – between greater wing and

maxilla

Lets infraorbital nerve (a branch of V2), artery and vein

Ethmoidal Foramina (anterior and posterior) – not in

the ethmoid bone, just above it in the frontal bone

○ Periorbita – periosteum on bones inside orbit

○ Orbital Septum – CT around eye that attaches tarsal plates to the rim of the orbit (made of fascia of tarsal plates)

Continuous with the periorbita; anterior to most things including the tarsal muscles

Medial and Lateral Palpebral Ligaments – thickening that connects tarsal plates to the sides of the orbit

○ Muscles

Levator Palpebrae Superioris – innervated by CN 3 (superior branch); opens upper eyelid

Tarsal Muscles

They are smooth muscle!

Origin Insertion Function Innervation

Superior Tarsal Levator palpebrae

superioris muscle

Superior tarsal plate Elevates upper lid

after fight or flight

Sympathetics (postganglionic cell

bodies in Superior

Cervical Ganglion) Inferior Tarsal (poorly developed)

Inferior rectus Inferior tarsal plate Widens palpebral

fissure

Orbicularis Oculi

Orbital Part – (not on eyelids), recruited when you close eyes tightly

Palpebral Part – (on eyelids), used for blinking

○ Glands of Eyelid

Tarsal (Meibomian) Glands – sebaceous (fatty) glands in the tarsus; more on upper lid

Lipid secretion lubricates edges of eyelids so they don‟t stick together

Forms barrier to lacrimal fluid (tears)

↑ tear viscosity and ↓ evaporation from surface of eye

Ciliary Glands – glands right by the cilium (eyelashes)

Glands of Moll – modified apocrine sweat glands on the margin of the eyelid

○ Empty onto edge of the eyelash

Glands of Zeis - sebaceous glands that open onto middle portion of hair follicle

Hordeolum (Stye) – tender, painful bump at base of eyelash or under or inside the eyelid

May arise from infected hair follicle at base of eyelash (staph aureus) or as complication with eyelid

inflammation

External Hordeolum – at base of eyelash involving hair follicle of eyelid (likely ciliary glands)

Internal Hordeolum – inflamed meibomian gland

○ Conjunctiva

Palpebral – portion of conjunctiva that lines inner side of eyelids

Innervated by V1 for upper and V2 for lower

Bulbar – portion of conjunctiva that is on eyeball (stops at corneoscleral junction)

Innervated by V1 for upper and lower

Fornices (superior and inferior) – the reflection of palpebral and bulbar conjunctiva; potential space with fluid

○ Lacrimal Apparatus

Lacrimal Gland – in superolateral orbit and secretes lacrimal into superior fornix

Lacrimal Fluid – contains lipid, aqueous and mucin; contains lysosyme (kills bacteria); provides nutrients

and oxygen to cornea

○ Makes up most of the liquid covering of the eye

Lacrimal Lake – area in medial canthus where lacrimal fluid collects

Lacrimal fluid travels from lacrimal gland medially across the conjunctiva to the medial canthus

Lacrimal Puncta – very small duct on medial edge of eyelids that comes into contact with the lacrimal lake

during blinking

Lacrimal Canaliculi – drains lacrimal puncta to lacrimal sac

Lacrimal Sac – top part of nasolacrimal duct that receives the fluids of the lacrimal canaliculi

Nasolacrimal Duct – travels inferiorly down to inferior meatus in the nasal cavity

Clinical Connection

Dry Eye – thin spots in tear film fail to protect eye

○ Causes – can be due to ↓ tear secretion from lacrimal gland or loss of tears due to excess evaporation

○ Symptoms – discomfort, visual fatigue, sensitivity to light, blurred vision

Sjogren’s Syndrome – inflammation of tear-secreting glands causing chronic dry eye and changes in tear

composition

Innervation

Sensory Component – capsule of gland

innervated by lacrimal nerve (V1)

○ Note - lacrimal nerve also carries

sensory fibers from lateral upper eyelid

and conjunctiva (just the V1 parts)

Parasympathetic Component – provides

secretomotor fibers to the parenchyma

○ Presynaptic Fibers – CN 7 gives off

branches to form the greater petrosal

nerve → nerve of pterygoid canal →

pterygopalatine ganglion

○ Postsynaptic Fibers – pterygopalatine ganglion → V2 branches (zygomatic → zygomaticotemporal

nerve) → hops off and goes to lacrimal gland

Sympathetic Branches – innervate vasculature of gland

○ Presynaptic Fibers – from lateral horn of T1-T4 → superior cervical ganglion

○ Postsynaptic Fibers – SCG → ICA plexus → deep petrosal nerve → nerve of pterygoid canal →

pterygopalatine ganglion → follow postsynaptic parasympathetics

○ Orbital Fascia

Fascial Sheath of the Eye (Tenon’s Capsule)

Envelops eye and distal part of EOMs from optic nerve to corneoscleral junction

Pierced by tendons of EOMs and continuous with their deep fascia

Suspensory Ligament of the Eye – continuous with fascial sheath of the eye

○ Attachments – starts at horizontal recti, goes inferior, connects with inferior

oblique and inferior rectus, ends on the other horizontal recti

○ Function – supports eye (forms hammock below eye)

Medial & Lateral Check Ligaments – strong expansions of fascial sheaths of m and l

rectus muscles

Attachments – orbit and lacrimal or zygomatic bones

Function – limits the movement of the m and l rectus muscles, limiting inward and

outward movement of the eye

○ Extraocular Muscles

Insertion – sclera of eye

Note – each of the rectus muscles inserts into sclera at ↑ distances from cornea starting with medial to

inferior to lateral to superior

“LR6 SO4 AO3”

Superior Oblique has a trochlea in the anteriormost and medial part of the orbit

Inferior Oblique originates on the anterior aspect of the orbit

Origin 1º Action 2º Action Innervation

Lateral Rectus Tendinous ring Abduction (primary) None CN 6

Medial Rectus Adduction (primary) None CN 3

Superior Rectus Elevation (primary) Adduction

Medial rotation

CN 3 (superior

branch)

Inferior Rectus Depression (primary) Adduction

Lateral rotation

CN 3

Inferior Oblique Maxilla

(anterior orbit)

Depression

Abduction

Medial rotation CN 3

Superior Oblique Sphenoid Elevation

Abduction

Lateral rotation CN 4

Actions

Except for the horizontal rectus muscles, the EOM actions depend on the orientation of the eye

Cross-Pairs Rule – change to opposite name to get pair

○ You need a pair of EOMs to look „straight up‟ or „straight down‟

○ To look straight up – superior rectus works with inferior oblique

○ To look straight down – inferior rectus works with superior oblique

○ Note – the rotational movements are not voluntary

Note – medial rotation (intorsion); lateral rotators (extorsion)

Actions of EOMs in isolation – see picture (right)

Testing EOMs – bring axis of eye into alignment with axis of the muscle

○ Horizontal rectus muscles are easy

○ Vertical rectus and oblique muscles are more difficult

Palsy Examples

○ LOOK AT HIS HANDOUT pg 153

Innervation

Occulomotor (CN 3)

○ Superior branch - levator palpebrae superioris, superior rectus

○ Inferior branch – medial rectus, inferior rectus, inferior oblique, ciliary ganglion

Trochlear (CN 4) – runs on medial side and dives into superior oblique

Abducent (CN 6) – runs on lateral side and dives into lateral rectus

○ Sensory Innervation

Ophthalmic Nerve (V1)

Lacrimal Nerve – travels on lateral side; (does not pass through tendinous ring)

Frontal Nerve – travels superior to eye; (does not pass through tendinous ring)

○ Becomes Supraorbital and Supratrochlear nerves

Nasociliary – travels medially passes through common tendinous ring;

○ Crosses lateral to medial, superior to CN 2

○ Nasociliary Root of Ciliary Ganglion – fibers pass straight through ciliary ganglion and don‟t synapse

○ Long Ciliary – sensory to eye

Sympathetic to papillary dilator muscle

○ Posterior Ethmoidal – (tough to see), sensory to sphenoidal & ethmoidal sinuses

○ Anterior Ethmoidal – sensory to nasal mucosa and face

Branches about halfway into orbit

Goes in between superior oblique and medial rectus

○ Infratrochlear – termination of ophthalmic nerve

Sensory to face

○ Ciliary Ganglion – a parasympathetic ganglion

Sensory

From trigeminal ganglion → CN V1 → nasociliary nerve (which

goes to skin of face) → gives fibers to

○ Long Ciliary Nerve – sensory to conjunctiva

○ Short Ciliary Nerve – sensory to conjunctiva

Goes through Ciliary Ganglion

Sympathetic

Lateral horn of T1-T4 → synapse in superior cervical ganglion → go in 2 pathways

○ Join nasociliary nerve and run along long ciliary nerve OR

○ Leave via sympathetic root → ciliary ganglion → short ciliary nerve

Function – motor to pupillary dilator

Parasympathetic

Brainstem → follow CN 3 → synapse in ciliary ganglion → travel via short ciliary nerve

Function – motor to pupillary constrictor and ciliary muscles

○ Horner’s Syndrome – interruption of sympathetic innervation to head and neck

Symptoms

Ptosis – drooping of eyelids due to paralysis of tarsal muscles (esp upper lid)

Pupillary constriction – paralysis of pupillary dilator

Enophthalmos (sinking of eye into orbit) – paralysis of orbitalis muscle in floor of orbit (vestigial)

Lack of sweating – lack of sympathetic (vasoconstrictive) innervation to BV and sweat glands

○ Arteries

Ophthalmic Artery – a branch of ICA; gives off a bunch of branches

Crosses lateral to medial over CN 2 with nasociliary nerve

Branches

○ Central Artery of the Retina – supplies optic retina (except cones and rods)

Dives into optic nerve and runs in the middle of it

○ Lacrimal Artery – goes with lacrimal nerve

○ Supraorbital Artery – supplies skin

○ Posterior and Anterior Ethmoidal Arteries – supplies ethmoidal canals?

○ Dorsal Nasal Artery – a terminal branch; supplies skin

○ Supratrochlear Artery – supplies skin

○ Veins

Superior Ophthalmic Vein – above eye; drains to ophthalmic vein then to cavernous sinus

Inferior Ophthalmic Vein – below eye; drains to ophthalmic vein then to cavernous sinus or to pterygoid

venous plexus Facial Vein – runs anterior to eye, inferiorly; anastomoses with the ophthalmic veins (thus can drain into

jugular system, pterygoid, or cavernous)

○ ICA Aneurysm and the Cavernous Sinus

ICA and CN 6 go right through the middle of the cavernous sinus, thus if ICA has ruptured aneurysm then

CN 6 will be the first thing to be affected

CN 3, 4, V1 & V2 also go through the cavernous sinus (more peripherally) and thus could be affected later

Pharynx ○ Objectives

Explain the anatomical location and functional significance of the pharynx

Give the boundaries of the three portions of the pharynx and list any important structures located in each of these areas What is the functional significance of the auditory tube? Where is it located?

Explain the location(s) of the lymphoid tissue found in the pharynx. Why is it important?

Explain how the muscles of the pharynx are organized. Give general origins and insertions for these muscles as well as their actions

Give all of the components of the pharyngeal plexus

What is the buccopharyngeal fascia? What is the retropharyngeal space? Why are these important?

○ Pharynx – fibromuscular half cylinder that is a common passageway for the GI and respiratory system

Goes from posterior aperture of the nose to the esophagus

○ Walls of the Pharnyx

Mucous Membrane – has sensory innervation (CN V2 & 9)

Submucosa –

Fibrous Layer (pharyngobasilar fascia) – provides support for muscles

Muscular Layer – constrictors are kinda circular, also longitudinal ones

Loose Connective Tissue - buccopharyngeal fascia

Then retropharyngeal space

○ Subdivisions of the Pharynx

Nasopharynx – base of skull to C2

Lies posterior to the nasal cavity

Choanae – opening between nasal cavity and nasopharynx

Pharyngeal Tonsil (Adenoids) – the superior portion of the nasopharynx abbuted to the occipital bone

Tubal Elevation – around superior entrance of auditory tube; made of cartilage

Auditory Tube (Pharyngotympanic Tube/Eustacian Tube) – connects middle ear to the nasopharynx

○ 2/3rds cartilage and 1/3 bone

○ Otitis Media – middle ear infection

Tubes in Ears – a drain put into the tympanic membrane to fix recurring otitis media

○ Otitis Externa – infection of the skin (which is really thin) of external ear canal

Skin there innervated by CN V3, 7 & 10

Oropharynx – C2-C4

Lies posterior to the oral cavity and is separated from it by the palatoglossal arches

Isthmus – opening between oral cavity and oropharynx

Palatoglossal Arches – fold of mucous membrane over the palatoglossal muscle

○ Right in line with the Uvula

Tonsilar Bed – area between palatoglossal arches (anterior) and palatopharyngeal arches (posterior)

containing the palatine tonsils

○ Innervation – CN 9

○ Blood Supply – facial artery

○ Palatine Tonsils – the „tonsils‟; lymphoid tissue

Palatopharyngeal Arches - fold of mucous membrane over the palatopharyngeal

muscle

Laryngopharynx – C4-C6

Lies posterior to the larynx

Piriform Fossa (recess) – indentation where things can get stuck and cause

irritation

Cricoid Cartilage – bulges into laryngopharnyx

○ Muscles of the Pharynx

Constrictors

Common Aspects

○ Insertion – pharyngeal raphe

○ Action – constrict consecutively and move bolus inferiorly

○ Innervation – CN 10

Superior Constrictor ○ Origin - pterygomandibular raphe (runs from pterygoid hamulus to mandible

posterior to 3rd

molar); is common connection of buccinator

Middle Constrictor ○ Origin – stylohyoid ligament & hyoid bone (superior margin)

Inferior Constrictor ○ Origin – lateral aspect of thyroid cartilage & cricoid cartilage

Longitudinals

Common Aspects

○ Insertion – blend in with constrictors of pharyngeal wall

○ Action – elevate the pharynx

○ Innervation – CN 10 except the stylopharyngeus which is

innervated by CN 9

Salpingopharyngeus

○ Origin – auditory tube

○ Covered in mucous membrane

○ Note – salpinx = tube

Stylopharyngeus ○ Origin – styloid process

○ Innervation – CN 9

Palatopharyngeus ○ Origin – soft palate

○ Covered by mucous membrane and makes the

palatopharyngeus arch

○ Blood Supply

Ascending pharyngeal artery, branches of maxillary artery, branches of facial artery

Also – inferior and superior thyroid arteries, and some lingual artery

○ Innervation

Pharyngeal Plexus – contains CN 10, CN 9 (stylopharyngeus portion), V2, sympathetic fibers (from cervical

sympathetic ganglion to BV), parasympathetic fibers (??to glands?, from CN X?)

Motor Innervation – CN X for constrictors and longitudinals except the stylopharyngeus (CN 9)

Sensory Innervation

Nasopharynx – V2

Oropharynx – CN 9

Laryngopharynx – internal laryngeal branch of CN 10

Note – innervation from cranial branch of accessory is basically called „CN X‟

Accessory Nerve – has two origins

○ Spinal component (cervical) – ventral horn of C1-C4, joins with cranial portion and goes through

jugular foramen and innervates SCM and trapezius

○ Cranial component – begins in nucleus ambiguous, joins with cervical portion and goes through

jugular foramen then joins with CN X

From here we just call it CN X

This stuff innervates pharynx and larynx

○ Temporomandibular Joint (TMJ)

Is a modified hinge joint and a synovial joint

Articular surfaces

condylar process

Postglenoid tubercle (of temporal bone) – limits posterior movement

Mandibular fossa (of temporal bone) – where condylar process rests

Articular tubercle (of temporal bone) – condylar process goes on top of this after jaw opens

Articular Disc – divides joint into two spaces

Inferior Joint Space – allows for hinge movement which is where the condylar process rotates on the

articular disc. This only allows jaw to open about 22 mm, after that protraction of the jaw starts

Superior Joint Space – allows for the gliding movement where the condylar process goes up and rests on

articular tubercle

What occurs when the mouth opens

Depression of the mandible – here the condylar process and articular disc do not move together

Protraction – here the articular disc and condylar process slide as a unit onto the anterior tubercle

More depression – condylar process continues to hinge on the articular disc to open jaw further

TMJ Syndrome – articular disc becomes detached from the chondyle??

This makes 2 clicks (during opening???)

Dislocated jaw – condylar process slides to anterior side of articular tubercle

Branchial and Pharyngeal Apparatus

○ Objectives

Describe a pharyngeal (brachial arch), pharyngeal (branchial) groove, pharyngeal (branchial) pouch, and pharyngeal (branchial)

membrane)

List the four structures that are found in a typical pharyngeal arch

List the skeletal, muscular derivatives and the innervation of each pharyngeal arch

Describe the fate of each of the branchial grooves, including the formation and fate of the cervical sinus Define and/or describe the fate of each of the branchial pouches or derivatives

Define and/or describe the point of origin, the migratory path, and the definitive situation of the thyroid gland

Describe the formation of the tongue

Describe the formation of the face from the five face primordial

Describe the formation of the palate and the congenital abnormalities that result in cleft palate and cleft lip

○ Everything here happens between weeks 4-8

○ Stomadeum – shallow depression that is the primitive mouth

Separated from pharyngeal foregut by the buccopharyngeal membrane

Buccopharyngeal membrane degenerates around 4th

week and forgut opens into amniotic cavity

○ Pharyngeal Apparatus – makes face, nasal cavities, mouth, larynx, pharynx and viscera of neck

Made by pharyngeal pouches, grooves and arches

Pharyngeal Arches – condensations of mesenchyme in between sets of opposed pharyngeal pouches and

grooves

Also contain neural crest cells that invaded in

Each contains

○ An arch artery

○ Cartilagenous rod – (the first cartilaginous rod is called the mandibular

prominence??)

○ Cranial nerve

○ Muscular component – the mesoderm part

Derivatives

○ Note - 1st Arch has two processes, the maxillary and the mandibular

Arch Skeletal Muscles Nerve Blood Vessel

1st

“Mandibular”

- “Meckel‟s cartilage” regresses

- malleus, incus

- sphenomandibular ligament

- muscles of mastication

- two tensors

- anterior belly of digastric

-mylohyoid

V3 Portions of

maxillary artery

2nd

“Hyoid” - “Reichert‟s cartilage” regresses

- stapes, styloid process

- stylohyoid ligament

- superior portion of hyoid

- muscles of facial expression

- stylohyoid

- posterior belly of diastric

- stapedius

CN 7 Stapedial Artery

3rd

- part of hyoid

- small cartilages in larynx (immobile)

- stylopharyngeus CN 9 ICA

4th & 6

th - large laryngeal cartilages - soft palate muscles

- pharynx and larynx muscles

CN 10 - left aortic arch

- right subclavian

Pharyngeal Pouches – out-pouchings of pharyngeal foregut that develop posterior to degenerating b mem.

Lined by endoderm

Each pouch takes the number of the arch above it

Pouch Derivatives

1st Elongates and forms middle ear, internal surface of tympanic membrane, auditory tube

2nd

Doesn‟t develop much

Forms tonsilar fossa, (invaded lymphatic tissue???)

3rd

Dorsal – forms inferior parathyroid (migrates a long way)

Ventral – forms thymus

4th

Dorsal – forms superior parathyroid

Ventral – forms ultimobranchial body (neural crest cells that invade thyroid and makes

parafollicular cells)

5th

Gets combined with 4th

Pharyngeal Grooves – grooves between the pouches, on the outside, opposite the pharyngeal pouches

Lined by ectoderm

Only one pair exist as an adult structure

Groove Derivative

1st deepens and forms the external auditory meatus (bony part) and the external surface of the

tympanic membrane

2nd

-4th

mesoderm inside 2nd

pharyngeal arch grows over all remaining grooves

Early on, cervical cyst is still present (a remnant of the groovs that is short lived)

Anomalies of Pharyngeal Pouches or Grooves

Branchial Sinuses – a persistent groove or pouch

○ Internal Branchial Sinus – usually happens at 2nd

pouch

○ External Branchial Sinus – if at 2nd

groove

Branchial Cyst – a persistent cervical cyst

Branchial Fistula – fistula between groove & pouch; can leak fluid; most common at 2nd

○ Structures that Develop from the Floor of the Pharynx

Tongue

Median Tongue Bud – a swelling in 1st arch inferior and between the two

lateral lingual swellings

Lateral (Distal) Lingual Swellings – 2 swellings in 1st arch that overgrow the

median tongue bed

○ Form the anterior 2/3rds of the tongue

Copula – a swelling on the 2nd

arch

Hypobranchial/Hypopharyngeal Eminence – a swelling that develops in the

3rd

and 4th arches

○ Grows over the copula and meets the lateral lingual swellings

○ Forms posterior 1/3rd

of the tongue

Terminal Sulcus – meeting point for anterior 2/3rds to posterior 1/3 of the

tongue

Median Sulcus – meeting point for the two lateral lingual swellings

Note – muscles of the tongue do not originate in pharyngeal wall, but migrate

there from occipital somites which are supplied by the hypoglossal nerve

Thyroid Gland

Thyroid Diverticulum – a diverticulum, not necessarily related to the pharyngeal pouches (more

medioventral), that becomes the thyroid

○ Extends through developing tongue, anterior to hyoid and anterior to larynx

Thyroglossal Duct – as the diverticulum extends, it remains connected to the pharynx via this

○ Only degenerates when the thyroid gets to its final spot

Foramen Cecum – in adult, this is the shallow, blind pit that marks where the thyroglossal duct started

Problems with Thyroid Development

○ Ectopic Thyroid Tissue – can be present anywhere along the thyroglossal duct

○ Thyroglossal Duct Cysts – can form anywhere along duct, including in tongue, ant. neck etc

○ Patent Thyroglossal Duct – stays open

Note – the pyramidal lobe of the thyroid is the ending of the thyroglossal duct

○ Formation of the Face

Note – everything here develops from the 1st pharyngeal arch

Note – mesenchyme from 2nd

pharyngeal arch invades the maxillary and mandibular prominences to make the

muscles of facial expression

Frontonasal Prominence – surrounds the developing forebrain, develops into forehead, ventral-most nose

and the philtrum (the medial groove of the upper lip)

Nasal Placodes – two lateral thickened areas of the frontonasal prominence

○ The lateral and medial portions swell and the center doesn‟t, it becomes the nasal pit

○ Lateral Nasal Swelling – swollen portion of lateral nasal placode

○ Medial Nasal Swelling – swollen portion of medial nasal placode

Both of these meet at the midline to make the Intermaxillary Segment

○ Intermaxillary Segment – gives rise to the philtrum, portions of the upper jaw, nasal septum and

primary palate

Maxillary Prominence – produced by proliferation of neural crest cells

Grow toward the lateral nasal swellings and meet at the nasolacrimal groove

Forms the lateral portion of the upper lip, upper cheek, most of maxilla and the palate

Mandibular Prominence – produced by proliferation of neural crest cells

The two mandibular prominences join together at midline, also meet the maxillary prominence above

Forms the lower lip, lower cheek, chin and mandible

○ Formation of the Palate

Occurs during 5th week

Incisive Foramen – junction of primary and secondary palates

Midline Raphe – marks the junction of the lateral palatine processes

Primary Palate – develops from the intermaxillary segment (part of frontonasal prominence)

Forms anterior portion of hard palate (anterior to incisive foramen)

Secondary Palate – the lateral palatine processes, which are prominences on the internal surface of the

maxillary prominences, enlarge and grow to meet in the midline

They fuse with the nasal septum

The anterior portion of the processes forms the hard palate and the posterior portion forms the soft palate

Cleft Lip – 1 out of 900 births; boys>girls

Occurs at the philtrum

Unilateral – failure of the maxillary and intermaxillary segments to fuse on one side

Bilateral – both sides

Cleft Palate – 1 out of 2500 births; girls>boys

Occurs at incisive foramen or the midline raphe

Primary (anterior) – failure of the primary palate to meet the secondary palate (incisve foramen)

Secondary (posterior) – failure of the lateral palatine processes to fuse together and with primary palate

Complete – no fusion of nothing (how is this different from

secondary??)

A – normal, B – unilateral cleft lip, C – unilateral cleft lip

and primary cleft palate, D – bilateral cleft lip and primary

cleft palate, E – isolated cleft palate, unilateral cleft lip and

secondary cleft palate

Nasal Cavity, Palate and Pterygopalantine Fossa ○ Objectives

Explain the external anatomy of the nose. What is responsible for the different shapes and sizes of noses?

Discuss the parts of the nasal septum. Give the blood supply and innervation to this structure

Explain the irregular contour of the lateral nasal wall. The inferior nasal conchae is a part of what bone? Give the blood supply and

innervation to the lateral nasal wall

Explain the shape of the ethmoid bone. What is the function of the paranasal sinuses? Describe the route of mucus drainage from

these sinuses

Discuss several common clinical problems associated with the nasal cavity (fractures, nosebleeds, chronic sinusitis) What bones make up the hard palate? What muscles make up the soft palate? What is the function of the uvulae?

Describe the complete course of the greater palatine nerve, the nasopalatine nerve. What components are in these nerves?

Give the source of the blood supply to the hard and soft palate

○ Nose – external nose and nasal cavity

External Nose – composed of 5 cartilages (4 paired, 1 unpaired) which determine shape of nose, and

fibrofatty tissue at the lateral end

Septal Cartilage – the 1 unpaired cartilage that runs on dorusm of external nose

Nares – anterior nasal openings

Dorsum – the „superior‟ surface

Root – where the bridge of the glasses sit

Apex – the tip of the nose

Ala – the winged, lateral portion

Nasal Septum – divides the two nares

Bony portion – made up of the two nasal, maxillary and frontal bones; superior to cartilages

Innervation

○ Dorsum → apex = CN V1

○ Ala – CN V2

Nasal Cavity – begins at the nares and ends at the posterior openings of the choana where it opens into

nasopharynx

Vestibule – entrance into nasal cavity (where you pick your nose); has course hair

○ Transition from skin of face to mucus membrane of nasal cavity

○ Innervation – nasal branches of infraorbital nerve (V2)

Mucoperiosteum – the mucus membrane of the nasal cavity

○ Special name because it is fused with the periosteum

○ respiratory mucus membrane with lots of glands and is highly vascular

Nasal Septum – composed of cartilage and very weak bone

○ Composition

Bony Portion

○ Perpendicular plate of Ethmoid – superior and anterior

○ Vomer – inferior and posterior

○ Nasal crest of maxilla (anterior) and palatine (posterior) – inferiormost part

Cartilagenous portion

○ Septal Cartilage – forms anterior-most portion of nasal septum

Note – the cribriform plate of the ethmoid bone forms a superior border of the nasal cavity

○ Innervation

Olfactory Nerve (CN 1) – goes through the cribriform plate and sends to olfactory bulb

○ Neurons are bipolar and have chemoreceptors in olfactory mucus membrane

○ Located in upper 1/3rd

of nasal cavity

Sensory – portions of CN V

○ Anterior Ethmoidal Nerve (septal branch) – V1 (a branch of the nasociliary nerve)

Courses anteriorly to almost the tip of the nose

○ Nasopalatine Nerve – V2

Comes out posterior to the olfactory nerve and courses obliquely on nasal septum

Goes into Incisive Foramen to supply the anterior hard palate

○ Blood Supply

Branches of Ophthalmic artery

○ Anterior Ethmoidal artery (septal branches) – follows anterior ethmoidal nerve

○ Posterior Ethmoidal Artery (septal branches) – comes out in the middle of the olfactory nerve

area and supplies middle septum

Branches of Maxillary artery

○ Sphenopalatine Artery – follows course of nasopalatine nerve (through incisive foramen)

A terminal branch of the maxillary artery

Note – each of those arteries has a corresponding vein

Lateral Nasal Wall – not flat to ↑ surface area to warm and moisten air (along with mucoperiosteum)

○ Concha – curved shelves of bone that extend from the lateral nasal wall

Inferior Nasal Concha – largest and most anterior; formed by seperate bone

Middle Nasal Concha – part of ethmoid bone

Superior Nasal Concha – part of ethmoid bone; smallest and most posterior

Note – in a vertical cross section you will often only see two concha at a time

○ Nasal Meatus – passageway deep to each concha

Inferior Meatus – (under inferior nasal concha) has opening for nasolacrimal duct

Middle Meatus – lots of openings

○ Hiatus Semilunaris – a semilunar groove with holes

Infundibulum – the anterior-superior most portion of it that receives the frontonasal duct

which drains the frontal sinus

Has an opening for the anterior ethmoidal air cells (more anterior superior)

Has an opening for the maxillary sinus (more posterior inferior)

○ Hiatus semilunaris is bounded by bulge superior to it, the ethmoid bulla, which is a protrusion of

the middle ethmoidal air sacs

Has openings from middle ethmoidal air sacs on it

Superior Meatus – has opening for posterior ethmoidal air cells

Sphenothmoidal Recess – above the superior nasal concha

○ Has opening for the sphenoidal sinus

○ Innervation

Olfactory Nerve – upper 1/3rd

Sensory – branches of CN V

○ Anterior Ethmoidal Nerve (septal branch) – V1, innervates anterior lateral nasal wall

○ Posterior Lateral Nasal Nerves – V2, come out posterior to olfactory nerve area and then goes

lateral across the concha

○ Inferior Nasal Branches of Infraorbital Nerve – V2, supplies inferior-anterior portion and

comes in inferiorly

○ Blood Supply

Exactly the same as the blood supply for nasal septum

○ except the sphenopalatine artery (a branch of the maxillary artery) gives off posterior nasal

branches that follow the posterior lateral nasal nerves and supply the concha

○ Paranasal Sinuses

Diverticula of the nasal cavity; mucus membrane is continuous

Enlarge with age

Named by the bone that contains them

Innervation – CN V

Frontal Sinus – most superior; drained by frontonasal duct, which opens

into the hiatus semilunaris at the infundibulum

Ethmoidal Sinuses (Air Cells) – the anterior and middle ones open into

middle meatus, the posterior one opens into the superior meatus

There are 8-12 air cells on each side

Sphenoid Sinus – most posterior; drains into sphenoethmoidal recess

(above superior nasal concha)

Maxillary Sinus – most inferior; drains into hiatus semilunaris (of middle meatus)

Inferior portion of sinus is very close to the upper molars

○ Maxillary Sinusitis – can manifest as upper molar pain

○ Absess of Upper Molars – can spread into maxillary sinus

Note – only the frontal sinus can drain into the nasal cavity easily by gravity

Thus mucus can build up and cause sinus headache or infection

If recurrent problem then a common surgery is to drill a hole in the maxillary sinus at the bottom of the

nasal floor to allow it to drain more easily (there will still be a potential place for mucus to pool however)

○ Palate

Separates the nasal cavity from the oral cavity

Hard Palate – bony portion that is more anterior

Lined by mucoperiosteum (continuous with surroundings)

Contains minor salivary glands (in mucous membrane)

Ruggae – ridges on top of mouth

Bones

○ Palatine Process of maxilla – forms the anterior portion

Most made by secondary palate

○ Horizontal portion of palatine bone – forms the inferior portion

Is this made by secondary palate too??

Incisive Foramen – marks juncture of the primary palate (anterior) and the two sides of the secondary

palate

○ Transmits the nasopalatine nerve (from nasal septum) and anastomosis of sphenopalatine and greater

palatine artery

Greater Palatine Foramen – transmits greater palatine N. A. & V.

○ Is in the horizontal portion of the palatine bone

Lesser Palatine Foramen – transmits lesser palatine N. A. & V.

Soft Palate – made mostly by muscles

Blends laterally with the pharynx

Function

○ When Elevated – closes the nasopharynx off from the oropharynx

○ When Depressed – closes the orocavity off from the oropharynx

Palatine Aponeurosis – sheet of dense CT that makes the core and provides stability for the soft palate

○ Attached to posterior margin of the hard palate (runs through soft palate?)

Muscles

Origin Insertion Action Inn

Levator Veli Palatini AT(cp) - medial -Palatine Apo. -elevate soft palate X

Tensor Veli Palatini AT(cp) - lateral -Palatine Apo. -travels around hamulus of medial

pterygoid plate first

-tenses soft palate (which helps it

elevate) V3

Musculus Uvulae (makes uvula)

Palatine Apo. The two parts blend together

posteriorly

Provides final closure between

nasopharynx and oropharynx

X

Palatoglossus Palatine Apo. Lateral tongue -depress soft palate X

Palatopharyngeus Palatine Apo. Blends with muscles of pharynx -depress soft palate X

○ AT(cp) – Auditory Tube, the cartilaginous portion

○ Note – all Tensors innervated by V3

○ Note – if uvula is too big then can cause sleep apnea, if it is too small

then poor closure

○ Note – the palatoglossus makes the anterior arch

Innervation

Branches of V2

○ Go through Palatine Canal – on lateral wall of nasal cavity

Greater Palatine – exits via greater palatine fossa and travels

anteriorly to hard palate

Lesser Palatine – exits via lesser palatine fossa and travels

posteriorly to soft palate

○ Nasopalatine – from nasal septum, enters through incisive foramen to innervate anterior hard palate

Blood Supply (for all of palate)

Branches of the Descending Palatine Artery which is a branch of Maxillary Artery

○ Go through Palatine Canal – on lateral wall of nasal cavity

Greater Palatine – follows course of greater palatine nerve

○ Continues and goes through incisive foramen to anastomose with the sphenopalatine artery

Lesser Palatine – follows course of the lesser palatine nerve

Note – these arteries are outside of bone on the mouth side of the palate

Note – veins follow same course

○ Pterygopalatine Fossa

Small pyramidal shaped space posterior and inferior to the apex of the orbit

Borders and Openings

Anterior Wall – posterior aspect of the maxilla

○ Inferior Orbital Fissure – on superior part; leads to infraorbital canal (which contains infraorbital

artery and nerve)

Posterior Wall – pterygoid process of the sphenoid bone

○ Foramen Rotundum – opens into the middle cranial fossa

Maxillary nerve leaves through here

○ Pterygoid Canal – in center

Contains the nerve and artery of the pterygoid canal

○ Pharyngeal Canal – most medial; leads to nasopharynx

Contains pharyngeal artery and nerve

Medial Wall – vertical portion of the palatine bone

○ Sphenopalatine Foramen – opens into the nasal cavity

Contains sphenopalatine artery and nasopalatine nerve

Lateral Wall – opens to the infratemporal fossa through the pterygomaxillary fissue

○ Pterygomaxillary Fissue – the inferior edges of the pterygopalatine fossa that come to a point

Maxillary artery comes in here, comes in lateral and goes medial

Posterior superior alveolar nerve and artery leave through here

Inferiorly

○ (Greater) Palatine Canal – goes to oral cavity

Transmits the greater and lesser palatine nerves & descending palatine artery

Contents

Third portion of maxillary artery and its branches

Maxillary nerve and its branches

Pterygopalatine ganglion and the nerve of the pterygoid canal

Maxillary Artery Branches

Note – comes in through the pterygomaxillary fissure

Posterior Superior Alveolar Artery – 1st branch

○ Exits PT fossa via pterygomaxillary fissure and pierces maxilla to supply upper teeth

Descending Palatine Artery – exits via palatine canal and divides into the greater and lesser palatine

arteries

Artery of the Pterygoid Canal – exits via pterygoid canal and supplies the nerve of the pterygoid canal

Pharyngeal Artery – exits via the pharyngeal canal and supplies nasopharynx

Infraorbital Artery – traverses the inferior orbital fissure and then exits via the infraorbital canal

○ Supplies the middle and anterior upper teeth and then supplies the face

Sphenopalatine Artery – exits via sphenopalatine foramen to supply the nasal cavity to supply nasal

septum (remember it gives off posterior nasal branches for lateral nasal wall)

○ Is the terminal branch

Maxillary Nerve (V2) Branches

Pure sensory

Exits PT fossa through the foramen rotundum

Nasopalatine – enters the sphenopalatine foramen

and innervates the nasal septum and anterior hard

palate

Infraorbital – enters the infraorbital canal and

innervates face, lateral nasal, cheek, lower eyelid

and upper lip

○ Posterior Superior Alveolar Nerve – branches

before infraorbital canal and innervates

posterior upper teeth

○ Anterior Superior Alveolar Nerve – goes

through infraorbital canal and then branches to

innervate anterior upper teeth

Pharyngeal – enters the pharyngeal canal and innervate mucus membrane of nasopharynx

Exit via Palatine Canal

○ Greater Palatine – exits palatine canal via the greater palatine foramen and innervates hard palate

○ Lesser Palatine – exits palatine canal via the lesser palatine

foramen and innervates soft palate

Pterygopalatine Ganglion

In PT fossa, suspended from maxillary nerve by two roots

Sensory Component

○ Fibers of V2 go through it to supply nasopalatine, posterior nasal,

greater palatine, lesser palatine and pharyngeal nerves

Parasympathetic Component

○ CN 7 → greater petrosal nerve → enters pterygoid canal to make nerve of the pterygoid canal →

enters pterygopalatine ganglion → synapses there → postganglionics are distributed via maxillary nerve

(V2) and also go up to V1 to innervate lacrimal gland

Sympathetic Component

○ lateral horn of T1-T4 → synapses in SCG → deep petrosal nerve → enters pterygoid canal to make

nerve of the pterygoid canal → enters pterygopalatine ganglion → is distributed with branches of V2

Extra Notes

Maxillary artery comes in through lateral side of PT fossa and exits on medial side

Maxillary nerve enters PT fossa from posterior side and exits as the infraorbital nerve

Functional Components of Cranial Nerves ○ Objectives

Review the components of a typical spinal nerve. How do those components compare and contrast to those of a cranial nerve?

Review the general plan for the sympathetic division of the ANS. Describe the primary pathways for sympathetic fibers to the head

and neck

Review the general plan for the organization of the parasympathetic division of the ANS. Which cranial nerves are associated with

the parasympathetic division of the ANS

Diagram all of the cranial nerves with a parasympathetic component. Identify the course of the preganglionic and postganglionic fibers, as well as the location and name of the ganglion associated with each nerve

What role does the trigeminal nerve serve in the autonomic control of structures in the head and neck? Identify portions of the

trigeminal nerve associated with the autonomic components of other cranial nerves.

○ General Types of Nerves in Neck

Afferents (Sensory) - pseudounipolar

Special Sense

Somatic – pain, touch and temp (can be mucus membrane in nasal cavity)

Visceral – „vague‟; in neck mostly innervation of mucus membrane

Efferents (Motor) – unipolar

Skeletal muscle – (from pharyngeal arch or somite, but this doesn‟t matter much)

Parasympathetic – smooth muscle, glands (cardiac muscle)

○ Have preganglionic and postganglionic fibers with an autonomic ganglia

○ Found with CN 3, 7, 9 & 10

○ General Sympathetic Visceral Efferent (in neck)

Effector – sweat glands

Pathway – lateral horn T1-T4 → ventral root → white ramus → paravertebral ganglion → cervical

sympathetic chain → synapse in any of the cervical ganglia → go to the plexus of one of the major arteries

(ECA, ICA) → travel along one of the branches of that artery → effector (often sweat glands)

○ Cranial Nerves

See extra table

CN Sensory Ganglion Parasympathetic Ganglion

3 Ciliary

5 Semilunar

7 Geniculate Pterygopalatine

Submandibular

9 Superior & Inferior Glossopharyngeal Otic

10 Superior & Inferior Vagal (Jugular) Terminal

Oral Cavity ○ Objectives

Define the boundaries of the oral cavity Review the innervation of the following structures: the lips, cheeks and gums

Review the five areas where lymphoid tissue forms “tonsils” around regions of the oral cavity and the formation of the tonsilar ring

Explain the anatomical considerations associated with the tongue and its sensory innervation

Know the organization, action, blood supply and innervation of the intrinsic and extrinsic muscles of the tongue

Review the suprahyoid muscles. What are their separate innervations? What is their collective action?

Review the three main pairs of salivary glands. Explain their location, the location of their duct(s) and their innervation

○ Boundaries

Lateral – cheeks

Superior – palate

Inferior - sublingual fossa and tongue

Anterior – lips and rima oris (opening of lips)

Posterior – oropharynx

○ Parts of Oral Cavity

Vestibule – space on buccal side of cheek and gums

Oral Cavity Proper – area on lingual side of teeth and gums; normally filled with the tongue

○ Review – Oropharynx contains palatoglossal arch (more anterior), palatopharyngeal arch (more posterior),

tonsilar bed and palatine tonsil and is innervated by CN 9

But the blood supply is the tonsilar branch of the facial artery

○ Lips

Vermillion Border – transition from red skin to normal skin

Philtrum – shallow vertical groove; the portion of the upper lip derived from the frontonasal prominence

(cleft lip occurs here)

Labial Frenulum – small fold of mucus membrane that is an attachment of lips to gums

Innervation

Upper Lip - Infraorbital Nerve (V2)

Lower Lip - Mental Nerve (V3)

○ Cheek

Boundaries – Medial boundary = Nasolabial Groove (the smile crease); Lateral Boundary = across zygo arch

Contents

Buccal Fat Pad – padding

Buccinator – a muscle of facial expression supplied by CN 7

Parotid Duct - pierces buccinator and opens as a papillae adjacent to the 2nd

upper molar in vestibule

Innervation

Infraorbital (V2)

(Long) Buccal Nerve (V3) – innervates inside and outside of cheek

○ pierces the buccinator

○ Gums (Gingivae) – fibrous CT covered with mucus membrane

Alveolar Gingivae – unattached part; the part between and encircling each tooth

Gingiva Proper – attached part; tightly affixed to the mandible or maxilla

Innervation – basically any nerve that passes the gums (don‟t focus on this)

External

○ V2 - posterior superior alveolar, anterior superior alveolar, infraorbital

○ V3 - inferior alveolar, mental, buccal

Internal

○ V2 – greater palatine, nasopalatine

○ V3 – lingual

○ Review – Innervation of Teeth

Upper Teeth = V2 → infraorbital → anterior superior alveolar & posterior superior alveolar (sometimes

middle)

Lower Teeth = V3 → inferior alveolar (then sometimes mental nerve)

○ Tongue

Function

Mechanical Digestion – keeps food between teeth, shape food into bolus, force bolus against soft palate

Move food into pharynx

Aid in phonation (formation of words) – if problem with tongue then slurred speech

Parts

Oral Portion (Body) – the unattached/movable part; in oral cavity; basically the anterior 2/3

Pharyngeal Portion (Root) – the attached (to hyoid) part; faces oropharynx; basically the posterior 1/3

Surfaces

Inferior Surface – covered by a thin layer of mucous membrane; can see blood vessels through it

○ Contains deep lingual veins and sublingual veins which are useful for drug delivery

○ Lingual Frenulum – line of mucous membrane from sublingual fossa to inferior tongue

If too short – tongue tied and can be surgically cut

If too long – often can touch nose with tongue

Dorsum (Superior Surface) – covered by thick mucous membrane and papillae

○ Papillae – specializations of mucous membrane; on anterior 2/3 of tongue

Filiform Papillae – increase texture of tongue for grip; most numerous, parallel to sulcus terminalis

○ No taste buds

Fungiform Papillae - club-shaped; have a singular taste bud; randomly placed

Folate Papillae – on lateral tongue; contain numerous taste buds

Vallate Papillae – 8-12 of them just anterior to sulcus terminalis; contains numerous taste buds

Note – no papillae on posterior 1/3, but there are taste buds there

○ Other Features

Median Sulcus – joining of the lateral tongue buds

Sulcus Terminalis – junction of anterior 2/3 (lateral tongue buds) with posterior 1/3

(hypopharyngeal eminence)

Foramen Cecum – old opening of the thyroglossal duct; right at point of sulcus terminalis

Lingual Tonsil – lymphoid tissue covered by mucous membrane (in posterior 1/3rd

)

Innervation

Anterior 2/3

○ Sensory – trigeminal ganglion → Lingual Nerve (V3)

○ Taste – geniculate ganglion → chorda tympani (CN 7) → Lingual nerve (V3 + CN 7)

Posterior 1/3

○ Sensory – Superior or inferior petrosal ganglia → lingual branch of CN 9

○ Taste

Superior or inferior petrosal ganglia → lingual branch of CN 9 → vallate papillae and taste buds of

posterior 1/3

Vagus (Lingual Branch) (superior & inferior vagal ganglion) → taste buds near epiglottis and very

back of tongue

Muscles

Innervation – CN 12 (Hypoglossal)

Intrinsic Muscles – create the body of the tongue

○ Arranged in bands (horizontal, longitudinal, vertical)

External Muscles – move body of tongue

○ Embryological Origin - Somites

Origin Insertion Action Inn

Hyoglossus Hyoid (superior part) Lateral tongue body Depress posterior and lateral

tongue

CN 12

Styloglossus Styloid Process Posterior-Superior

tongue body

Retract & elevate posterior

tongue

Genioglossus Mental Spine Fans out and attaches to

body of tongue

Protudes tongue

○ Clinical Application

Test function of CN 12 by asking patient to stick out tongue and see if it deviates to one side

○ Note – palatoglossus also helps move tongue? It is innervated by CN X

Blood Supply

Lingual Artery – from ECA; landmark – dives deep to the hyoglossus

○ Dorsal Lingual – to posterior tongue

○ Deep Lingual – termination of lingual artery; supplies body of tongue

○ Sublingual – anterior branch of lingual artery; supplies the sublingual

gland

○ Salivary Glands

Parotid Glands – largest salivary gland

Parotid Duct – crosses masseter → pierces buccinator → opens into

vestibule adjacent to 2nd

upper molar

Innervation

○ Parasympathetic – CN 9 → lesser petrosal → synapse in otic ganglion → joins with auriculotemporal

(V3) → jumps off and goes to parotid

○ Sympathetic – T1-T4 → synapse in SCG → follows BVs to parotid

Can go through otic ganglion if it wants

Submandibular Glands – located along body of mandible on either side of mylohyoid

Submandibular Duct – crosses under lingual nerve (nice landmark) in sublingual fossa → touches

sublingual gland → opens in sublingual papilla (adjacent to lingual frenulum)

Sublingual Glands – in floor of mouth, deep to tongue

Opens via many ducts directly into the sublingual fossa

Innervation to Submandibular and Sublingual Glands

Parasympathetic – CN 7 → chorda tympani → joins with lingual nerve (V3) → synapses in submandibular

ganglion

○ Postsynaptics then either go to submandibular gland or to the sublingual gland (where they meet with

lingual nerve again?)

Sympathetic – T1-T4 → synapse in SCG → follows BVs to parotid

○ Can go through submandibular ganglion if it wants

○ Structures of the Sublingual Fossa

Sublingual Gland

Submandibular Duct

Lingual Nerve (V3) – landmark – crosses over submandibular duct

Hypoglossal Nerve

Sublingual Artery – in anterior part

○ Muscles to Suprahyoid Region

Action

raise hyoid, tongue and floor

steady hyoid for independent tongue movements

If hyoid fixed then they can help open mouth

Names – stylohyoid, mylohyoid, geniohyoid, digastric

Larynx ○ Objectives

Describe the cartilaginous skeleton of the larynx

Explain the orientation of the membranes that act to support the cartilages of the larynx Describe the internal anatomy of the larynx. Where are the vestibular folds? Where are the vocal folds?

Explain the location, innervation and action of each of the intrinsic muscles of the larynx

Review the blood supply and innervation to the mucous membrane that lines the larynx

Explain how the larynx works during phonation. What anatomical features of the larynx may affect the quality of your voice?

○ General

Larynx – organ of speech; holds airway open

Anteriorly covered by infrahyoid muscles and the thyroid gland

Adjacent to C3-C6; visible as laryngeal prominence

Anterior to laryngopharynx

Larger in men

Completely covered in mucous membrane (inside and out)

○ Anatomy

Cartilages

Unpaired

○ Thyroid Cartilage – largest; is open posteriorly

Made by 2 plates that come together and form superior thyroid notch and superiorly the laryngeal

prominence Superior Horn – thyrohyoid membrane attaches here

Inerior Horn – articulates with the cricoid cartilage

○ Cricoid Cartilage – only part that forms complete ring

Narrow anterior arch; wider and flatter posterior lamina (like signet ring)

Posterior superior portion articulates with arytenoid cartilages

Articulates with inferior horn of thyroid cartilage

○ Epiglottis – leaf shaped, elastic cartilage

Articulates with internal anterior surface of thyroid cartilage

Paired – (made of hyaline cartilage?)

○ Arytenoid Cartilages – pyramidal shape

Muscular Process – lateral extension; attachment for posterior and lateral cricoarytenoid muscles

Vocal Ligament – anterior extension; attachment for vocal ligament

○ Corniculate Cartilages – small cartilages that lie on the apex of the arytenoid cartilages

○ Cuneiform Cartilages – small nodules of cartilage in the aryepiglottic fold

Membranes

Outside

○ Thyrohyoid Membrane – causes movement of the hyoid to translate to movement of the thyroid

Pierced by the internal laryngeal nerve and the superior laryngeal artery

○ Cricothyroid Membrane

Medial Cricothyroid Membrane – exterior; just connects thyroid to cricoid

Lateral Cricothyroid Membrane (Conus Elasticus) – interior; connects vocal ligament to cricoid

○ Cricotracheal Membrane – goes all the way around

Inside

○ Quadrangular Membrane – creates tube called the Laryngeal Inlet

Attachments – lateral margins of epiglottic cartilage & anterolateral margin of arytenoid cartilage

Aryepiglottic Fold – superior margin of quadrangular membrane covered in mucous membrane

Vestibular Ligament – inferior margin of quadrangular membrane

Vestibular Fold – vestibular ligament covered in mucous membrane

○ Conus Elasticus (Lateral Cricothyroid Membrane) – body of it connects to cricoid

Vocal Ligament – superior margin of conus elasticus; connects arytenoids to anterior thyroid

Vocal Fold – vocal ligament covered in mucous membrane

Chambers of Interior Larynx

Rima Glottis – space between the two vocal ligaments

Vestibule – interior area of larynx superior to the vestibular fold

Ventricle – diverticulum of mucous membrane between the vestibular and vocal folds

Infraglottic Cavity – interior area of larynx inferior to the vocal fold

Muscles

All are skeletal muscle

Extrinsic – move the entire larynx

○ Suprahyoid Muscles – elevate larynx

○ Infrahyoid Muscles – depress larynx

Intrinsic – act on laryngeal cartilages to change vocal ligament for speech

○ All are covered by mucous membrane

○ Innervated by recurrent laryngeal

Posterior Cricoarytenoid – causes abduction of the vocal ligaments by pivoting arytenoid

Lateral Cricoarytenoid – causes adduction of the vocal ligaments by pivoting arytenoid

Transverse & Oblique Arytenoids – causes adduction of vocal ligaments by sliding arytenoid

Thyroarytenoid – slackens vocal ligament

○ Fibers follow the vocal ligament and thus connect arytenoid to the thyroid cartilage

○ When they contract it brings the arytenoid and thyroid cartilages closer together

○ Innervated by external branch of superior laryngeal/external laryngeal

Cricothyroid – pivots thyroid cartilage (pivots at posterior horn) down towards the cricoid cartilage

and thus lengthens/tightens the vocal ligament

Swallowing – larynx elevates (extrinsic muscles) and epiglottis is pushed into the posterior 1/3rd

of the

tongue causing it to be passively bent to close the laryngeal inlet

Blood Supply

Superior Laryngeal Artery – branch of superior thyroid artery which is branch of ECA

○ Pierces thyrohyoid membrane with the internal laryngeal nerve

Inferior Laryngeal Artery – branch of inferior thyroid artery which is a branch of thyrocervical trunk

Nerve Supply

Superior Laryngeal Nerve – branch of vagus

○ Internal (branch) Laryngeal Nerve – pierces thyrohyoid membrane

Sensory – mucosa of larynx superior to vocal folds

Parasympathetic – glands of larynx superior to vocal folds

○ External (branch) Laryngeal Nerve Motor – to cricothyroid (and inferior constrictor)

Recurrent Laryngeal/Inferior Laryngeal Nerve – branch of vagus

○ Note – in tracheoesophageal groove and passes under lower border of inferior constrictor

○ Sensory – mucosa of larynx inferior to vocal folds

○ Parasympathetic – glands of larynx inferior to vocal folds

○ Motor – to all intrinsic laryngeal muscles except the cricothyroid

○ Concepts

When inhaling the vocal cords must be open

When talking the vocal cords must be closed tightly

Laryngitis or loosing voice – inflammation and edema prevents vocal cords from closing tightly

Cross-Sections ○ Objectives

Review key features of plain films and CT or MRIs of the head and neck

Identify the key landmarks of the head and neck to be used as guides in cross-sectional anatomy of the region

Review representative levels of the head and neck and identify specific structures listed in the handout at each level

○ Through Eye

Nasal septum (just bone here, the perpendicular plate of the ethmoid), nasal bone, ethmoidal air cells,

sphenoid sinus, ICA (just lateral the sphenoid sinus, in cavernous sinus), dural sinuses, squamous part of

temporal bone, petrus portion of temporal bone, occipital bone, optic nerve (thus will see medial and lateral

rectus), temporalis muscle, superficial temporal vessels

○ Through Nose

Maxillary sinus, facial vessels, nasal septum (carilage anteriorly, vomer posteriorly), inferior nasal septum,

inferior meatus, nasopharynx, superior constrictor (because we are at level of auditory tube), auditory tube

(looks like a little line), prevertebral muscles (just posterior to constrictors), ICA (medial), IJV (lateral),

vertebral arteries,

Lateral pterygoid plate, medial pterygoid muscle (medial to LPtP), lateral pterygoid muscle (lateral to LPtP

and has muscle fibers in horizontal plane), maxillary vessel branches (between coranoid process and head of

mandible), temporalis (on coranoid process), masseter (lateral to ramus of mandible), coranoid process, head

of mandible, superficial temporal artery (posterior to head of mandible)

○ Just above upper teeth

Incisive foramen, hard palate, soft palate, pharyngeal space, pharyngeal constrictor, vertebral artery, C1, dens,

ICA (medial), IVJ (lateral), buccinator (more medial than you would think), buccal fat pad, masseter (lateral to

ramus), ramus of mandible, medial pterygoid (medial to ramus), parotid gland, retromandibular gland and

ECA right near or in parotid gland, muscles of facial expression (little slivers)

○ Through Tongue

Tongue, oropharynx, pharyngeal constrictors, palatine tonsils (on border of oropharynx), prevertebral muscles

(posterior to constrictors), buccinator, masseter (lateral to ramus), ramus of mandible, medial pterygoid

(medial to ramus), ECA (more anterior), ICA (more posterior), IJV (lateral to ICA and ECA), parotid with

EJV or retromandibular vein going through it, SCM, vertebral artery

○ Through Lower Chin

Body of mandible, extrinsic tongue muscles, sublingual gland (looks like fat), mylohyoid (running vertically

here (attaching to mandible), submandibular gland (caps mylohyoid), oropharnyx, constrictors, prevertebral

muscles, vertebral artery, EJV (linked to SCM), SCM, parotid gland (with retromandibular vein in it), IJV,

ECA, ICA, facial vessels

○ Below Mandible

Mylohyoid (forming floor of oral cavity), anterior belly of digastric, root of tongue, epiglottis (anterior to

pharynx), laryngopharynx, constrictor, vertebral arteries, platysma, submandibular gland (with facial vessels

in it), ECA, ICA, IJV, SCM (with EJV linked)

○ Below C4

Epiglottis, vestibule of larynx, thyroid cartilage (looks different), infrahyoid muscles, laryngopharynx, inferior

constrictor, EJV, SCM (with EJV), IJV, CCA, anterior jugular (anteriorly)

○ C6

Trachea, esophagus, thyroid gland, infrahyoid muscles, SCM, vertebral artery, anterior scalene, brachial

plexus (white tissue), middle scalene, EJV (near brachial plexus), IJV, CCA

Development of the Eye and Ear ○ Objectives

Eye

Define and/or describe: optic vesicle, optic cup, optic fissure (choroid fissue), lens placode, lens pit, lens vesicle

Define and/or describe: hyaloid artery (central artery of the retina), hyaloid canal

Define and/or describe the three major layers of the eye and list the component structures found in each

Describe the major steps that occur in the formation of the lens. What induces formation of the lens?

Describe the formation of the anterior chamber of the cornea. What induces the differentiation of the cornea?

Describe the formation of the iris, ciliary body, retina

Ear

Describe the formation of the internal ear and external ear

Define and/or describe the three anatomical subdivisions of the ear; the otic placod and list the structures derived from it; the

membranous labyrinth and the bony labyrinth; endolymph and perilymph

Describe the relationships between the utricle and related semicircular ducts and endolymphatic duct. Describe the relationship

of the saccule and the cochlear duct

Briefly describe the function or the neural transducers found in the semicircular ducts, the utricle, and the cochlear duct

Briefly describe the formation of the tympanic cavity from the 1st pharyngeal arch. What is the developmental history of the

middle ear ossicles?

Briefly describe the formation of the external auditory canal from the 1st branchial cleft

Define pinna (auricle). What is the developmental history of the auricle?

Distinguish between “nerve deafness” and “conduction deafness”. List at least one congenital cause of each

What is congenital cholesteatoma?

When is the ear most susceptible to teratogens?

Explain the developmental history of any/all structures observed in microanatomy lab exercises

○ Eye

Summary of Derivations

Note – adult eye is composed of 3 coats, but each has multiple embryological origins

Surface Ectoderm (from head) – makes corneal epithelium, lens, epithelium of eyelids

Neuroectoderm (from forebrain) – retina, optic nerve, pupillary muscle, epithelium of iris and ciliary body

Mesoderm – extrinsic eye muscles, internal structures of the eyelids

Neural Crest (migrated in) – ciliary muscles, choroid, sclera, corneal endothelium

Development

Apparent at day 22 (week 3)

Optic Grooves – shallow grooves on the anterolateral surface of developing forebrain; become:

Optic Vesicles – further evagination of the optic grooves that project outward? towards the surface

ectoderm of the head

○ Optic Stalk – remaining connection of forebrain to optic vesicle

○ Eventually, the optic vesicle contacts the surface ectoderm of the head and this initiates formation of:

Lens Placode – thickening of surface ectoderm

Optic Cup – invagination of the optic vesicle

○ Anterior portion of vesicle ends up touching the posterior portion

○ Intra-retinal Space – small space between the anterior and posterior parts of cup

Lens Development

○ Lens placode grows inward toward the optic vesicle and forms the Lens Pit which continues to

invaginate and forms the Lens Vesicle which detaches from the surface ectoderm

○ Thus, lens development depends on interaction between the optic vesicle and surface ectoderm

Note – removal of optic vesicle prevents lens formation

Note – you can make optic vesicle tissue from other stuff and use the new stuff to stimulate lens dev

Pax-6 is important for lens development

○ Lens forms in concavity of the optic cup

Lentiretinal Space – space between developing lens and anterior portion of the optic vesicle

○ Becomes filled with gelatinous matrix that eventually forms the vitreous body

○ Cytodifferentiation

Fibroblast Growth Factor – causes non-specialized surface ectoderm cells of lens placode to

become lens cells

○ Secreted by the developing retina around WK 6

○ Causes cells to exit cell cycle and become postmitotic

Elongate along rostro-caudal axis of lens

Synthesize crystallins and become transparent

Cells closest to retina (posterior) become Primary Lens Fibers and form the Lens Nucleus

Lens continues to elongate and grow via division of lens fibers in the equatorial margin and fibers

from here are called Secondary Lens Fibers

○ Blood Supply

Hyaloid Artery – supplies developing optic cup and lens

○ From ICA → ophthalmic artery → hyaloid artery

○ Grows into the ventral surface of the optic stalk in the Choroidal Fissure

○ As eye grows, the vitreous separates the lens from the retina, but the hyaloid artery still supplies

lens until it no longer needs blood and then the anterior portion of the hyaloid artery degenerates

The posterior portion becomes the Central Artery of the Retina

Retinal Development

○ Outer (Posterior) Wall of optic cup – becomes the RPE

Becomes heavily pigmented around 5 weeks

○ Inner (Anterior) Wall of optic cup – thicker; becomes the 9 layers of neural retina

Cells in this layer differentiate between 6 and 7 weeks

Initial Differentiation

○ External Limiting Membrane – separates outer neuroblastic cells

from the intraretinal space

○ Outer Neuroblastic Layer – ↑ cell density; becomes photoreceptors

and such

○ Inner Neuroblastic Layer – ↓ cell density; becomes RGCs and such

○ Internal Limiting Membrane – separates inner neuroblastic cells from vitreous

Later Differentiation

○ RGCs develop first and photoreceptors develop last

○ The cells of the other layers differentiate

○ Axons of RGCs collect on inner surface and grow towards optic stalk, and exit the eyeball

This makes the optic stalk larger and it then becomes called the Optic Nerve

○ Note – the two walls become „fused‟ by week 7 (RPE cells contact outer segments of photoreceptors)

Development of the Choroid and Sclera

○ Mesenchymal Jacket – loose mesenchyme largely derived from neural crest cells that covers the

external surface of the optic cup

These cells respond to inductive signals from the RPE and form two layers

○ Inner Layer – forms the vascular choroid coat

○ Outer Layer – forms the fibrous scleral coat

Development of the Iris and Ciliary Body

○ Develop from anterior rim of optic cup

○ Iris develops from the ciliary body?

○ Three Cellular Origins (from anterior rim of optic cup)

Cells from the anterior rim of the mesenchymal jacket proliferate and form a bulge near lateral lens

→ form the Ciliary Muscles

Pigmented cells of posterior wall of optic cup (the RPE) cover the bulge → forms pigmented layer

Cells of the innermost region of the retinal layer also cover the bulge → forms non-pigmented layer

○ Ciliary Process – just a squiggly area of the ciliary body formed by folding of the retinal layer

Secretes the zonular fibers of the suspensory ligament of the lens

○ Continued proliferation of the pigmented and non-pigmented layers eventually forms the posterior iris

○ Anterior Iris is made by ectomesenchymal cells

○ Note – non-pigmented cells of the iris become pigmented later in life

○ Neural Crest cells migrate into the iris and form the dilator pupillae and sphincter pupillae

Development of the Cornea

○ Three Sources

Surface ectoderm covering the anterior optic cup

Mesenchyme surrounding the optic cup

Neural crest cells derived from the lip of the optic cup

○ The optic vesicle secretes inductive signals and stimulates the surface

ectoderm

These cells secrete primary stroma made of collagen fibrils, hyaluronic

acid and have ↑ hydration

1st wave of neural crest cells then migrate into primary stroma and form

the corneal endothelium (innermost)

2nd

wave of neural crest cells invade the primary stroma and degrade the

hyaluronic acid into secondary stroma, which has a ↓ hydration level

(thus more transparent)

○ Bowman’s Membrane – outer acellular membrane secreted by outer corneal epithelium

○ Descemet’s Membrane – inner acellular membrane secreted by inner corneal endothelium

○ The endothelium continues to actively transport water out of the cornea to make it transparent

This is thyroxin dependent

Chambers of the Eye

○ Mesenchyme surrounding optic cup invades area between lens and future cornea around 6th week

Outer Layer – becomes part of corneal stroma

Inner Layer – forms iridopupillary membrane (a thin membrane over the pupillary opening)

○ This degenerates and forms a cavity for the posterior chamber

○ Ear

Inner Ear Development

1st part of ear to develop (22 days)

Otic Placodes - develop as thickening of surface ectoderm dorsal to the 2nd

pharyngeal arch

Otic Pits – further invagination of the otic placodes

Otic Vesicles – pinching off of the otic pits

○ Utricular Region – Upper elongated compartment of the otic vesicle

Forms the vestibular apparatus

○ Saccular Region – lower elongated compartment of the otic vesicle

An elongation off of this forms the chochlear duct and spiraling progresses to 2 ¾ turns

Derivations

○ A small group of epithelial cells migrate medially toward the neural tube and form CN VIII Spiral

Ganglion ○ Another group of epithelial cells migrate to floor of cochlear duct to form sensory hair cells of the

organ of corti

○ Neural crest derived cells migrate to

the floor of the otic vesicle and form

the basilar membrane and

supporting cells of the organ of corti

Development of the Cochlear Duct

○ Reissner’s Membrane – form the roof

of the developing cochlear duct

○ Mesenchyme condenses around

cochlear duct forming a cartilaginous capsule

Dorsal and ventral regions begin to vacualize to become perilymph filled scala vestibule and tympani

Poles of the cochlear duct become anchored to the cochlear canal at the spiral lamina and spiral

ligament

The cartilaginous capsule becomes a bony encasement at around 16 weeks

Development of the Vestibular Apparatus

○ Begins around 6 weeks with the cochlear duct

○ Portions of the wall of the utriclar compartment flatten and fuse

○ Adhesion points undergo apoptosis and form the 3 semicircular canals

○ Ampullae develop too

Middle Ear Development

Mesenchyme adjacent to the ectoderm of the 1st and 2

nd arches condense to form the cartilaginous

precursors of the auditory ossicles (bones)

1st pharyngeal arch elongates to form tubotympanic recess, which engulfs the ossicles and forms the

middle ear cavity

1st pharyngeal groove ectoderm invaginates

inwards to touch tubotympanic recess

This forms the tympanic membrane which is

thus made by outer ectoderm, mesenchyme and

inner endoderm

External Ear Development

Derived from the initial invagination that was

dorsal to the 1st pharyngeal arch

That area develops 6 nodular masses of

mesenchyme called auricular hillocks

Hillocks 1-3 – derived from 1st arch

○ Form anterior external ear

Hillocks 4-6 – derived from 2nd

arch and form

posterior external ear

Eye ○ Objectives

Identify the three tunics (major layers) of the eye and sup-components of each

Identify the chambers of the eye; boundary structures for each and contents of each

Identify the layers of the cornea and cellular composition of each

Identify the layers of the choroids region of the eye

Identify the ciliary body and detail its function

Identify the components of the iris and pupil and relate their structure to their function Identify the Canal of Schlemm (scleral venous sinus), its function and its importance in clinical diseases of the eye

Identify the lens of the eye and zonules of Zinn

Describe the production, flow pathway and absorption of the aqueous humor

Identify the retina and its ten layers

Identify the photoreceptors of the eye

○ I‟m abbreviating this lecture

○ Refractile Elements – cornea, aqueous humor, lens, vitreous

○ Note – photoreceptor cells send out graded? neural impulses

○ Development of the Eye

Optic Stalk – part of outpocketing that isn‟t the optic vesicle

Forms from outpocketing of neural tube that has an enlargement at the end called the optic vesicle

Optic Cup – optic vesicle invaginates and the anterior wall smushes up against the posterior wall

○ Posterior Wall – becomes the pigment epithelium of the retina, ciliary body and iris

○ Anterior Wall – becomes the neural retina

Lens Vesicle – an inbudding of surface epithelium that buds off; forms lens

Mesoderm between the anterior and posterior wall and forms the supporting coat and vascular coat

Surface ectoderm – forms eyelids, conjunctiva, outer epithelial layer of cornea

○ Layers of Eye

Tunica Fibrosa - outer (cornea and sclera)

Uveal/Vascular Coat - middle (iris, ciliary body & choroid)

Retinal Coat – RPE and neural retina

Retinal Pigment Epithelium – covers the posterior surface of the iris, the ciliary process, and the entire

posterior wall of the eyeball in front of the choroid

Ora Serrata – where the neural retina stops and the ciliary body begins

○ Suspensory Ligaments of the Lens (Zonules of Zinn) – attach lens to ciliary body

○ Chambers of the Eye

Anterior Chamber – bounded by iris and cornea

Posterior Chamber – bounded by lens, iris and ciliary body

Vitreous Chamber – bounded by the lens and the posterior wall of the eye

○ Microanatomy of the Eye

Tunica Fibrosa

Sclera – posterior 5/6

○ Continuous with the dura mater covering the optic nerve

○ Episclera – external surface; dense layer of vascularized CT

Attached to dense CT called Tennon’s Capsule

○ Scleral Stroma – sheets of collagen fibers in different orientations parallel to the surface

Contains malanocytes, fibrocytes and amorphous ground substance

Contains elastic fibers

Relatively avascular and high water content makes it opaque

○ Lamina Fuscia – inner surface; fine collagen fibers that blend with the choroid layer

○ Lamina Cribrosa – where optic nerve pierces the sclera

Cornea – anterior 1/6

○ Provides 2/3 of focusing power of eye

○ Relatively avascular, receives nutrients from aqueous

○ Low hydration level to keep it clear

○ Limbus – marks juncture of sclera and cornea

○ Layers

Epithelium - stratified squamous non-keratinizing epithelium; about 5-6 cells thick

○ Cells connected by desmosomes

○ Have microvilli to maintain tear film

○ Densely innervated with pain receptors, for blinking and lacrimation

○ Basal Cells – capable of rapid mitotic division (7-10 days) to replace corneal tissues

Bowman’s Membrane – thin acellular layer

○ Contains randomly arranged collagen fibers closely adherent to basement membrane of epi.

○ Protective barrier against bacterial invasion

Lamina Propria - thickest layer

○ Contains regularly arranged collagen fibrils, fibrocytes and amorphous ground substance

Descemet’s Membrane – thick basement membrane of the corneal epithelium

Corneal Epithelium - simple squamous inner lining of cornea

○ Cells linked by desmosomes and occluding junctions

○ Function – actively transports water out to maintain clarity

Secretes Descemet‟s membrane (linked to it by hemi-desmosomes)

Uveal (Vascular) Coat – vascular structures of the eye

Choroid Layer – vascular layer of the eye; starts at ciliary body and covers posterior eye

○ Fenestrated capillaries allow tissue fluid to circulate freely in the CT

○ Layers

Suprachoroid Layer – adjacent to inner sclera

○ loose CT with elastic fibers anchoring it to sclera

Vessel Layer – CT with higher collagen content

○ Contains lots of choroidal arteries and veins

○ Malanocytes – absorb scattered light

Choriocapillaris - single layer of wide fenestrated capillaries

○ Nourish tissue, including outer 1/3 of retina

Bruch’s (Glassy) Membrane – network of collagen and elastic fibers

○ Between basement membrane of choriocapilaris and RPE

Iris

○ Layers

Anterior Limiting Layer – discontinuous layer of stromal cells

○ Contains fibroblasts and malanocytes

Stroma – vascularized loose CT

○ Contains fibroblasts and malanocytes

Muscular Layer – 2 bands of muscle

○ Sphincter Pupillae – circular band of smooth muscle near posterior border of iris

↓ size of pupil

Under parasympathetic control

○ Dilator Pupillae – radially oriented smooth muscle near posterior border of iris

↑ size of pupil

Under sympathetic control (look for person‟s pupils to enarge if excited)

Posterior Epithelium - double layer of cuboidal pigmented cells

○ Cells heavily pigmented with melanin to only let light through pupil

○ Eye Color – caused by varying amounts of melanin in the stroma of the iris

Reduced melanin in stroma → blue eyes

Increased melanin in stroma → brown eyes

Ciliary Body – thickening of choroid that forms a ring around the eye, just behind the iris

○ Loose CT, fenestrated capillaries and smooth muscle

○ Epithelium - double cuboidal epithelium

Superficial non-pigmented layer

Deep Pigmented layer Apical surfaces of each layer face each other and thus the two basement membranes abut each other

Two layers connected by desmosomes

○ Ciliary Processes – ridges at the inner edge of the ciliary body

Zonules of Zinn – connect here

○ Ciliary muscles attach to choroid anteriorly (huh?)

○ Functions

Produce Aqueous Humor

○ Aqueous Humor – filtered out of capillaries of the ciliary processes into the posterior chamber

Transported out of the interior of the ciliary body by pigment epithelial cells which are

surrounded by a basement membrane that forms blood-aqueous barrier

Microtubular Meshwork – fibrous channels at lateral aspect of ciliary body which receive

aqueous about to be drained from the eye

Canal of Schlemm – drains aqueous; located near attachment of ciliary body to sclera

Lined with simple squamous epithelia

Fluid goes into aqueous veins then to the conjunctiva then venous blood

Flow – posterior chamber → anterior chamber → microtubular meshwork → canal of schlemm

→ aqueous veins → conjunctiva → venous blood

Regulate Shape of Lens

○ Ciliary Muscles

Controlled by parasympathetic system

Contraction causes release of tension on zonules of Zinn

Attach at the limbus

○ Eyes at rest (focused at distance) – elasticity of choroid pulls the zonules tight and backwards

○ Eyes focusing on something near – ciliary muscles pull things forwards and release tension

This ↑ focusing power of the lens by ↑ its curvature

The Retinal Coat

Note – photoreceptors point away from incoming light

Cell Types – require special stains to distinguish

○ Photoreceptors –

○ Bipolar Cells – 2nd

order neurons; transmit to 3rd

order

○ Horizontal Cells – 2nd

order neurons; interconnect photoreceptors laterally

○ Amacrine Cells – send signal from many bipolar cells to fewer RGCs

○ Ganglion Cells – 3rd

order neurons

Encode whether a contour or edge is present, its color, brightness and exact position in space

○ Muller Cells – glial cells that extend through all 10 layers of the retina

Nuclei found in inner nuclear layer; processes wrap around photoreceptors

Layers

○ Retinal Pigment Epithelium – makes blood/retina barrier

Single layer of cuboidal-columnar cells

○ Apical surface has microvilli and cylindrical cytoplasmic sheaths

○ enclose photoreceptors to nourish and phagocytose pieces shed pieces of their outer segments

○ Contain melanin (prevent light scatter)

Goes over ciliary body and posterior iris

Bruch’s Membrane – attaches base of RPE cells to the choroid

Detached Retina – no firm connection between RPE and retina and so this is where retina can detach

○ Photoreceptor Layer – contains rods and cones

Parts

○ Outer Segment – the light-sensitive region

Constantly turned over by being sloughed off

Dense vertical stacks of membrane bound discs that are

infoldings of the cell membrane

Contain Vit A derivative photopigment made of retinene

and opsin

Rhodopsin – rod pigment; for dim light

Photopisin – 3 types of cone pigments

The shape in cones → broad and tapered

The shape in rods → long, narrow and straight

○ Cilium – connects outer segment to inner segment

Made of non-motile cilia

Microtubules of cilia form 9 peripheral doublets

○ Inner Segment – contains most of the organelles

Membrane of this region contains a lot of K+ channels that are

active during phototransduction

○ Outer Segment – thinner segment between the inner segment

and the cell body

Muller cell processes surround this portion and attach by tight junctions

More prominent in rods

Sometimes called external limiting membrane

○ Cell Body – contains the nucleus

○ Inner Fiber Layer – thin part that expands at the end and makes contact

with other layers

Spherule – expansion of this layer in rods

Pedicle – expansion of this layer in cones

Distribution

○ Fovea Centralis – depression in retina with a huge concentration of cones

Devoid of blood vessels

Other layers of retina are thinner here

○ Rods mainly in periphery

Transduction

○ Light causes hyperpolarization of the photoreceptors

○ cGMP and Ca+ dependent modulation of Na+ channels in photoreceptor membrane

○ External Limiting Membrane – not really a membrane, just the zonula adherens junctions of the

cytoplasmic processes of Muller cells with the photoreceptors

○ Outer Nuclear Layer – where the nuclei of photoreceptor cells are

Nuclei are at different distances and so it looks like it is thick stratified, but it isn‟t

○ Outer Plexiform Layer – contains the synaptic processes of the photoreceptors (in contact with bipolar

or horizontal cells)

No cell bodies, relatively unstained

○ Inner Nuclear Layer (Bipolar Layer) – contains cell bodies of bipolar, horizontal and amacrine cells

○ Inner Plexiform Layer – contains processes of bipolar, horizontal, amacrine and ganglion cells

○ Ganglion Cell Layer – contains cell bodies of retinal ganglion cells

○ Retinal Axon Layer – contains the unmyelinated RGC axons

They become myelinated when they get to the optic nerve

○ Internal Limiting Membrane – not a true membrane

Basement membrane of the Muller cells

Neural Activity

○ Information sent in retina is mainly graded hyperpolarization and depolarization, not real APs

○ RGCs are the only things to make full APs (frequency changes)

○ Remember – photoreceptors are hyperpolarized by light and thus chronically release neurotransmitter

Light brighter than environment causes a ↓ in rate of transmitter release (and visa vers)

Optic Disc (Papilla) – a blind spot caused by the axons of RGCs leaving the retina to form optic nerve

Fovea – visual acuity at its best

○ ↑ density of RGCs and cones; ↓ thickness of other layers

○ little diffusion; appears yellow (macula lutea)

Blood Supply

○ Retinal Artery and Vein – enter eyeball at optic disc and split to go either supierioly or inferiorly

Supplies the inner 2/3rds of the retina with capillaries (the rest is supplied by choroid)

○ Diabetic Retinopathy – uncontrolled plasma glucose in eye causes vascular edema and altered retinal

and choroidal vasculature

Can cause scar tissue induced retinal detachment, edema, vascular leakage, neovascularization

○ The Lens

1/3 of the focusing power of the eye

Zonules of Zinn – composed of microfibrils and are attached to the equator of the lens and ciliary body

Avascular and contains no CT

Anterior Surface

Lens Capsule – made of collagen and proteoglycans

Simple cuboidal epithelium

Lens Fibers – cells that lost their nucleus and organells and form fibers

○ Packed with crystallins

○ Fibers connected together by knob and socket like depressions, tight junctions and gap junctions

○ Fibers at center of the lens persist throughout life (not replaced)

Germinal Zone – at the equatorial rim; here cells divide slowly and are added to the rim

○ Vitreous

Contains amorphous ground substance (GAGS) and thin, randomly oriented collagen fibrils and water

Adheres to the peripheral retina and the ciliary epithelium

Ear ○ Objectives

Identify the three components of the ear (ie outer, middle and inner ear). Identify the boundaries and components of each. Relate

structure to function

Identify the structure of the tympanic membrane (eardrum)

Differentiate between the components of bony labyrinth and membranous labyrinth

Identify the region of the cochlea, including the basilar membrane, helicotrema, osseous spiral laminal and spiral ligament

Describe the fluid that is found within bony labyrinth (perilymph) and that found in the membranous labyrinth (endolymph) and how and where each is formed and removed

Identify the three major divisions of the cochlear canal

Identify the boundaries of the cochlear duct

Identify the components of the organ of Corti including: tectorial membrane, outer and inner phalangeal cells, outer and inner pillar

cells, cochlear hair cells

Identify the spiral ganglion cells as they are embedded in bony modiolus

Identify the maculae of the utricle and saccule

Identify the components of cristae ampullaris, including the cupula, the vestibular hair cells, and the sustentacular cells

○ Parts

External Ear – collects sound vibrations and directs them towards sensory transducers

Auricle – involved in locatization of sound in space

○ Irregular plate of elastic cartilage covered by thin skin with hair and sebaceous glands

External auditory meatus – connected to temporal bone

○ Outer 1/3 - elastic cartilage continuous with cartilage in auricle

○ Inner 2/3 – formed by temporal bone

○ Thin skin with Ceruminous Glands (modified apocrine sweat glands) that make ear wax

Tympanic membrane – sounds displaces this and vibration is transmitted to middle ear bones

○ 2 layers of collagen

○ Outer side – covered by layer of very thin skin

○ Inner side – covered by simple squamous epithelium

Middle Ear – transduces sound waves into mechanical displacement of inner ear

Tympanic cavity – air filled cavity; resonance chamber

○ Lateral wall – tympanic membrane

○ Medial Wall – bony labyrinth

○ simple squamous epithelium with thin LP

○ Fluid filled and thus not compressible

○ Ossicles – a „lever system‟ that transmits movements of the tympanic membrane to inner ear

They ↓ amplitude, but ↑ force („impedance matching‟)

The Bones

○ Malleus – attached to tympanic membrane

○ Incus – between the other two

○ Stapes – attached to the Oval Window of the vestibule (of inner ear)

Eustacian tube – connects tympanic cavity with nasopharynx

○ Equalizes pressure between the outside air and the middle ear cavity

○ Made of cartilage

○ Covered by pseudostratified columnar ciliated epithelium

○ Otitis Media – middle ear infection, often caused by bacteria getting in through eustacian tube

Inner Ear – contains receptors for hearing and vestibular sensation

Bony labyrinth – a series of bony channels

○ Filled with perilymph

Like extracellular fluid (↑Na, ↓K)

○ Vestibule – large central cavity that has the two

membrane covered openings, the Round and Oval

windows

○ Cochlear Canal – a single pathway extending

anteriorly from the vestibule

Spirals for 2.75 turns around the modiolus

Modiolus – bone that houses BVs, cell bodies

of spiral ganglion cells and the *acoustic

branch of CN 8

Spiral Lamina – thin bony ridge extending

laterally from modiolus

○ Semicircular Canals – 3 looped canals on

posterior side of vestibule

Ampulla – dilation at portions connecting to the vestibule

Membranous Labyrinth – membranes suspended in the perilymph in the canals of the bony labyrinth that

contain the specialized structures for hearing and vestibular sense

○ Delicate CT lined with simple squamous epithelium

○ Utricle and Saccule are membranous sacs in the vestibule

○ All membranous ducts are continuous and contain endolymph

Endolymph – similar to intracellular fluid (↓Na, ↑K)

○ Endolyphatic Duct – where old endolymph drains into; off of utricle and saccule

○ Auditory Sensory Apparatus

Cochlear Duct – suspended medially in cochlear canal

Roughly triangular in cross section and divides canal into three sections

○ Scala Vestibuli (above) & Scala Tympani (below) – filled with perilymph

Lined with thin CT that is continuous with periosteum of cochlear canal

Helicotrema – connection between scala vestibule and scala tympani at apex of cochlear canal

○ Scala Media (Cochlea) – filled with endolymph; central partition of cochlear canal

Walls

○ Reissner’s (Vestibular) Membrane – roof

2 layers of simple squamous epithelium separated by a basement membrane

○ Stria Vascularis - lateral wall; source of endolymph

Thin layer of CT and highly vascular epithelium

○ Basilar Membrane – floor

Amorphous ground substance with transversely oriented filaments

Lower surface covered by columnar epithelium

Supports organ of Corti (spiral ligament and osseous spiral lamina support it)

Has different width and stiffness at different points along its length which determine which

frequency a specific point along its legth is most sensitive to

High frequency sounds – localize near base (beginning) of cochlea where it is narrowest

and most taught

Low frequency sounds – localize near apex (end) of cochlea where it is narrowest and

least taught

Organ of Corti – rests atop the basilar membrane

Tunnel of Corti – triangular shaped tunnel midway across the basilar membrane

○ Base formed by basilar membrane but walls formed by supporting cells

Pillar Cells – form walls of tunnel of Corti

○ Cone-shaped columnar cells with basilar nuclei

○ Rigid due to lots of microtubules

Phalangeal Cells – tall columnar cells

○ Phalanx – cytoplasmic process that extends along side the hair cells and support the base of them

○ Sensory Hair Cells

Inner Hair Cells – sensitive to small changes in sound intensity

○ About 3500, short, goblet-shaped cells

○ Arranged in a single-row

○ Each has <70 stereocilia

○ Innervated by CN 8 (each cell innervated by about 20 fibers)

Outer Hair Cells – respond best to low intensity sounds

○ About 20,000, cylindrical, columnar cells

○ Arranged in 3 rows kinda like a „W‟

○ Each has >100 stereocilia

○ Tips of tallest stereocilia are embedded in the the tectorial membrane

○ Innervated by CN 8 (lots of cells innervated by a single nerve fiber)

Note – CN 8 supplies spiral ganglion???

○ Tectorial Membrane – sheering of this membrane triggers electrical impulses in embedded hair cells

Gelatinous membrane composed of keratin-like protein

Made by cells of spiral laminae

Vibrations to Nerve Impulses

Pressure waves travel down external auditory meatus and displace tympanic membrane

Vibrations of tympanic membrane are ↓ in amplitude and ↑ in force by ossicles (impedence matching)

Vibrations transferred to oval window which causes wave in perilymph to cochlear canal in scala vestibule

→ helicotrema → scala tympani and dissipate at round window

○ During this pathway vibrations are transferred to the basilar membrane

Movement of the basilar membrane causes „shearing motion‟ of hair cell stereocilia with respect to

the tectorial membrane

This causes change in polarization in the hair cells and sends an impulse in CN 8 Spiral Ganglion

cells in the modiolus

Impulses go to the auditory cortex of CNS

Coding Attributes of Sound

Sound Amplitude – loud sounds produce larger amplitude waves that stimulate more hair cells

Sound Pitch

○ Volley Theory – sound frequency encoded by frequency of APs in 8th

nerve

For sounds >200 Hz fibers still fire in phase, but skip groups to take turns

○ Place Theory – sound frequencies have a different optimal spot to be received on the basilar membrane

Higher frequencies → base; low frequencies (which can travel farther) → apex

Prolonged exposure to sounds at a certain frequency can cause degredation of the cells receiving it

○ Vestibular Sensory Apparatus

Composed of 2 endolymph filled sacs and 3 endolymph filled semicircular ducts arising from ampulla

Semicircular Canals and Apulla

All connect to the utricle

Each has an expanded region called the ampulla at one of its junctions with the utricle

Cristae Ampullaris – a raised transverse ridge in the ampulla

○ Types of Cells in Cristae

Sustentacular Cells – tall columnar supporting cells

Sensory Hair Cells

○ Innervated by neurons of Vestibular (Scarpa’s) Ganglion in the modiolus

These neurons terminate in vestibular nuclei of the brainstem

○ Type I Cells – flask-shaped cells with stereocilia similar to inner hair cells

Flanked by a single non-motile kinocilium

Receive funnel-shaped nerve endings

○ Type II Cells – cylindrical cells with stereocilia similar to outer hair cells

Flanked by a single non-motile kinocilium

Receive bouton-like nerve endings

Cupula – gelatinous glycoprotein that covers the sensory hair cells

○ Movement in the plane of a given semicircular canal causes stereocilia to bend against the inertia

of the endolymph and the cupula

This causes change in polarization of hair cells and APs to vestibular ganglion cells

Utricle and Saccule

Both in the vestibule of the bony labyrinth

Macula – 3x3mm patch of sensory epithelium

○ Structure

Columnar Supporting Cells Sensory Hair Cells – similar to those in cristae

Otolithic Membrane – gelatinous glycoprotein that covers the surface of the hair cells

Otoliths – crystalline bodies of calcium carbonate that are suspended in the otolithic membrane

○ Function

Inertia of otolithic membrane and otoliths causes bending of stereocilia and change in polarization

Senses head position

Senses linear acceleration

Saccule – vertical plane

Utricle – horizontal plane

○ Basic Structure of Hair Cells

Similar in auditory and vestibular system and between cell types

Features

Turn mechanical stimulation into electrochemical impulses

Stereocilia arranged hexagonally

○ Composed of actin filaments surrounded by paracrystalline structures

○ Graded in height – tallest and shortest at the opposite ends of the bundle

○ Tips of stereocilia have Tip Links which are protein bridges that extensively crosslink them (huh??)

Are at extreme angles and thus allow for unidirectional responsiveness of the cilia

Kinocilium – adjacent to tallest row of cilia (except in mammals)

APs

○ Depolarization occurs when cilia are bent in the direction of the tallest cilium

This also tightens the tip links

○ Resting APs – steady rate when the cilia aren‟t bent

○ Hyperpolarization occurs when the cilia are bent away from tallest cilium

This also loosens the tip links

○ Cilia probably are directly coupled with membrane ion channels

○ Blood Supply to the Ear

ECA – supplies external ear, middle ear and bony labyrinth

Labarynthine Artery – a branch of the basilar artery that supplies the inner ear

Anterior Vestibular Artery – supplies most of the semicircular canals

Common Cochlear Artery – supplies cochlea, utricle, saccule and the rest of

the semicircular canals

Note – hair cell‟s high metabolic rate requires lots of blood and lack can cause

damage

○ Disorders of Ear

Hearing Loss

Destruction of hair cells or 8th nerve fibers

○ Hair cells sensitive to antibiotics, diuretics and salicylates

○ Chronic exposure to loud sound of constant frequency can cause excitotoxicity of hair cells and 8th

fiber

Fixation or calcification of ossicle

Rupture or puncture of tympanic membrane

Tumors of 8th nerve or the ganglion

Vestibular Dysfunction

Drug toxicity – antibiotics or diuretics

Tumors

Menier’s Disease - Overproduction or blockage of endolymph causing abnormal stimulation of all types of

hair cells

Symptoms – vertigo, nausea, vomiting, abnormal sound perception, sometimes temporary deafness

Oral Cavity ○ Objectives

Describe and identify the component parts of the lip (skin, vermilion border, labial mucosa, labial glands & orbicularis oris muscle).

Relate their structure to function.

Identify and describe the component parts of the tongue (lingual mucosa, filiform, fungiform and vallate papillae, taste buds, skeletal

muscles, lingual salivary glands and von Ebner glands). Relate their structure to their function. Describe and integrate the component parts of a tooth. (enamel, dentin, cementum, pulp, anatomic root and crown, neck and clinical

crown). Relate structure to function.

Describe the composition and structure of the periodontal ligament and relate it to its function.

Identify the distinguishing features of the gingiva and gingival sulcus associated with the alveolar processes bearing teeth.

Describe the composition of primary and secondary dentition.

Describe the development of the typical tooth. Identify the formation and origins of dental lamina, enamel organ, dental papillae,

dental sac, ameloblasts and enamel, odonoblasts and dentin, epithelial root sheath and the process of eruption.

Describe how the structural characteristics of odontoblasts, ameleoblasts and cementoblasts relate to their function.

Compare and contrast the composition, formation, structure and function of enamel, dentin and cementum.

Compare and contrast Tome's fibers (odontoblastic processes), Tome's processes, dentinal tubules and enamel rods.

Describe the composition and location of dental pulp.

Describe what is a salivary gland and identify the groups of minor glands and major glands. Describe and identity the parotid, submandibular and sublingual glands. Integrate their characteristic structure to their function.

Describe and integrate serous and mucous acini, serous demilunes, intralobular ducts (intercalated and striated) and interlobular

ducts into the structure of all salivary glands.

○ Oral Cavity

Boundaries

Anterioly – lips

Posteriorly – palatoglossal folds

Laterally – buccal cavities

Contents – lips, tongue, teeth, salivary glands

○ Lips

Orbicularis Oris – allows them to move

Regions

Cutaneous - stratified squamous keratinized epithelium with hair follicles and sweat glands

Vermillion Border – red region due to tall dermal papillae with capillaries

○ stratified squamous para-keratinized epithelium

○ Lacks sweat glands, needs to be moistened occasionally

Oral Mucosa – internal

○ Lining Mucosa – lines most of oral cavity (including soft palate)

mucosal stratified squamous epithelium on moderately dense irregular CT

Have submucosa and glands

○ Masticatory Mucosa – lines regions exposed to pressure and shear forces (ex. gingiva and hard palate)

parakeratinized to keratinized stratified squamous epithelium on tightly bound dense irregular CT

Lack submucosa and glands

○ Tongue

stratified squamous non-keratinizing epithelium and thin LP

Contains serous and mucous glands and lingual tonsils

Muscles

Extrinsic

○ Responsible for moving tongue in and out of mouth and side to side

○ Genioglossus, hyoglossus, styloglossus and palatoglossus

Intrinsic

○ Arranged in intertwining bundles: longitudinal, transverse and oblique

○ Responsible for changing shape of tongue (phonation)

Surface

Sulcus Terminalis – V-shaped groove that divides anterior 2/3rds from posterior 1/3rd

Foramen Cecum – depression at point of V that marks old thyroglossal duct

Posterior 1/3 – contains root of tongue and lingual tonsils

Lingual Papillae – mucosal projections on dorsum

○ Have a vascular core of CT covered by stratified squamous non-keratinizing epithelium

○ Types

Filiform Papillae – narrow conical; most common

○ Give tongue its texture (increase friction); tip has keratinized epithelium

○ no taste buds

Fungiform Papillae – mushroom shaped portion contains taste buds

○ Location – lateral edges of tongue

○ non-keratinized epithelium with redder color

Foliate Papillae – leaf shaped

○ Not well developed in humans (lose taste buds by age 3)

○ Location – margin of tongue

Circumvallate Papillae – like a mushroom cloud; there is a moat surrounding each

○ 9-12 of them just anterior to the sulcus terminalis

○ The protrusion has central core of CT covered by non-keratinized epithelium

○ Taste buds located in groove created by protrusion and on its sides

○ Serous Glands of von Ebner – located deep to the protrusion and drain into the moat

○ Taste Pore – narrow opening formed by surrounding epithelial cells

○ Taste Buds – spherical structure composed of 60-80 cells; approximately 3000 of them

Taste Hair – long, slender microvilli of receptor cells that extend out of taste pore

Receptor Cells – life span of 10-14 days

○ Progression – basal cells (IV) → intermediate cells (III) → light cells (II) → dark cells (I)

○ Taste receptors located on microvilli

○ In synaptic contact with nerve fibers of CN 7 (anterior 2/3) and CN 9 (posterior 1/3)

And Vagus

Each nerve fiber receives from about 5 taste buds

Each taste bud is innervated by about 50 nerve fibers

Taste Sensations – caused by specific taste receptor cells

Note – each taste bud can discern all tastes, but some kinda specialize

Note – tastants are continually washed away by salivary glands

Sweet – tip of tongue; 5 different types: for sugars, alcohols, ketones, amino acids, and sucrose

○ Caused by binding of G-Protein coupled receptors → ↑cAMP → ↓ permeability of K+

Salty – front sides; by salt and inorganic salts: NaCl, NaF, NH4Cl, MgCl2

○ Caused by direct entry of Na+ into receptor cell

Sour – sides; H+ concentration

○ Caused by decreased permeability of K+

Bitter – back of tongue; stimulated by quinine or organic alkaloids of toxic plants

○ Mainly received by circumvallate papillae

○ Caused by binding of G-Protein coupled receptors → ↑IP3 → ↑ intracellular Ca++

Umami – for monosodium glutamate

○ Salivary Glands

Make 1-1.5 quarts of saliva a day

Function – initiates digestion, lubricates swallowing, protection, aids food tasting

Contents – mucus, proteins, salts, salivary amylase, lingual lipase, lysosyme (antibacterial), lactoferrin, IgA

Minor Salivary Glands – reside within oral mucosa and tongue

Small short tubular glands

Major Salivary Glands – the Parotid, Submandibular and Sublingual glands

Have ducts that drain directly into oral cavity

Innervated by both sympathetics and parasympathetics

General Structure

○ All are compound tubuloalveolar

○ Organized into lobes and lobules separated by CT septa

○ Secretory Portion – serous, mucus or mixed

○ Acinus – come in tubes or alveoli; surrounded by myoepithelial cells that aid in secretion

○ Duct System

Intralobular Ducts ○ Function – resorb Na & Cl ions

Secrete bicarbonate ions

○ Intercalated Ducts – drain acini and tubules

simple cuboidal and some myoepithelial cells

Hard to recognize; smallest are same size

as acini

○ Striated Ducts – merge together at end

simple cuboidal to low columnar

More reddish due to more mitochondria

and membrane infoldings

Interlobar Ducts - between lobules

○ surrounded by CT – diagnostic

Interlobar Ducts – larger ducts; between lobes

of gland

○ Surrounded by CT of large septa

Main Terminal Duct – drains entire gland

Parotid Gland

○ Largest; 30% of volume; located over angle of mandible

○ Secretory portion is tubule and acini

○ Secretion – serous – diagnostic

Reddish staining

Granules rich in: salivary amylase, IgA (inactivates antigens), antimicrobial proteins, lactoferrin,

Na, Cl

○ White adipocytes mixed in - ↑ with age

○ Ducts

Intercalated ducts – drain acini and tubules; same size as acini and therefore difficult to see

Striated ducts - light pink staining, striations visible (due to mitochondria)

○ Not surrounded by CT

Interlobular Ducts – normal; surrounded by CT, located between lobules

Main Terminal Duct (Stetsen‟s Duct)

Submandibular Gland ○ Produces 60% of saliva; Located under mandible in floor of mouth

○ Similar in structure to parotid gland

○ Main excretory duct (Wharton‟s) exits on frenulum of tongue

○ Serous acini : Mucus acini – 5:1 – diagnostic

Mucus cells secrete mucin rich in sialic acids and sulfates

Pellicles – mucins and proteins in saliva form protective coat on teeth to protect against acids, retain

moisture, and regulate adherence of bacteria

Lack of saliva causes tooth decay, yeast infections and inflammation

Sublingual Gland ○ Located inerior to tongue

○ Similar in structure to others

○ Secretes through multiple ducts on sublingual fold

○ Predominantly mucus, but some serous demilunes – diagnostic

○ Function – mucin helps lubricate food and also to form the pellicle

○ Duct system – shorter and harder to find

○ Teeth

Permanent – 32; Deciduous (baby teeth) – 20

Types – incisors (for cutting), canines (for puncturing & holding), molars (for crushing and grinding)

Structure

Crown – part visible in oral cavity

Root – part buried in alveolus of bone

Neck – junction between the crown and root

Pulp Chamber – space in center of tooth; filled with vascular areolar CT

○ Rich in proteoglycans and glycoproteins

○ Odontoblasts – line the pulp and produce dentin

○ Root Canal – longer portion; carries BVs and nerves

○ Apical Foramen – opening at root tip for entry of BVs and nerves

Periodontal Ligament – dense irr. CT that holds tooth in socket by connecting alveolar bone to cementum

Sharpey’s Fibers – bundles of collage in the ligament

Structurally it is a fibrous joint (a gomphosis), functionally it is a synarthroses

Gingiva – supports tooth and seals it off oral cavity from CT

parakeratinized → keratinized epithelium (Masticator mucosa)

Gingival Groove – space adjacent to the tooth, deep to the gingival

Junctional Epithelium – where epithelium attaches to enamel surface by hemidesmosomes (where?)

○ Forms sealing barrier around neck of tooth

Body of Tooth

Enamel – covers crown; hardest surface in body

○ Made of 96% hydroxyapatite crystals and 4% water and organic material (enamelins and amelogenin)

○ Enamel Rods – the organization of the enamel; kinda „keyhole‟ shaped

Enamel is laid down by ameloblasts from dental surface outward, the rods are remnants of that

Interrod Region – place where hydroxyapatite crystals have different orientation

Dentin – makes up bulk of tooth; 2nd

hardest surface in body

○ Made of 70% hydroxyapatite crystals and 25% organic material

○ more elastic and thus prevents tooth from fracturing

○ Note – pulp cavity slowly becomes smaller throughout life

○ Odontoblasts – produce dentin; continually lay down new dentin

Odontoblastic Processes – cytoplasmic processes that extend through the dentin to the enamel-

dentin junction Dentinal Tubule – space where the odontoblastic processes fill

Predentin – unmineralized organic matrix that will become mineralized soon

Cementum – on outside of dentin on the root

○ Made of 50% hydroxyapatite crystals and 50% organic material; makes it about as strong as bone

○ Cementocytes – in lacunae of cementum matrix; just like osteocytes

Cell processes run through canaliculi and reach vessels in the periodontal space

○ Cementoblasts – line outer surface at periodontal ligament

Secrete cementum throughout life

○ Tooth Formation

Begins at 6-8 weeks

Bud Stage

Oral ectoderm proliferates and forms dental lamina; 10 tooth buds are formed on each jaw

Ectomesenchyme – derived from neural crest; surrounds the bud

Cap Stage

Early Phase – proliferation increases structure and it forms three layered structure

○ Outer Enamel Epithelium – epithelium on outer surface

○ Inner Enamel Epithelium – epithelium on inner surface

○ Stellate Reticulum – cells in between those layers

Late Phase ○ Ectomesenchyme condenses to form dental papilla which give rise to odontoblasts and dental pulp

○ Cervical Loop – rim where two ectodermal layers make a sharp bend

○ Dental Sac – vascular tissue in tooth germ formed by ectomesenchyme

○ Note – ectodermal connection to surface is lost & permanent bud arises

Bell Stage – characterized by 4th layer of cells in enamel

Increases in size and forms „bell shape‟

Stratum Intermedium – forms between stellate reticulum and inner enamel epi.

Outer enamel epithelium breaks down and dental sac collapses on stratum intermedium

○ This causes stratum intermedium to induce the inner epithelium to differentiate into

ameloblasts

This differentiation induces the inner cells of the dermal papillae to differentiate

into odontoblasts which start producing dentin

Enamel is laid down after the dentin to make dentinoenamel

junction

Appositional Phase – deposition of the dentin and enamel

○ Odontoblasts are pushed away from the dentinoenamel junction as

the dentin is deposited but the distal end of the cell remains at the

dentinoenamel junction to form odontoblastic processes

Unmineralized dentinal matrix is laid down, then mineralized

○ Note – crown forms before the root

○ Ameloblasts – lay down enamel similarly, but when unmineralized

matrix is laid down then the apical process is pinched down to form

the Tomes process which doesn‟t continue through enamel

Root Formation – occurs after the crown is completed

Hertwig Epithelial Root Sheath – forms the root

○ Created from cervical loop epithelium that extends downward

○ Stratum intermedium does not form below dentinoenamel junction

Thus the inner layer below does not form ameloblasts

○ Odontoblasts form and deposit dentin

○ Outer and inner epithelial layers disintegrate in cervical loop region and ectomesenchyme cells come in

contact with the dentin and differentiated into cementoblasts to deposit cementum on outside of root