POSTERIOR

&

ANTERIOR

TRIANGLE OF NECK

Dr. H.A.JaafarDr. H.A.Jaafar

Al-Nahrain University-Al-Nahrain University-

college of Medicine college of Medicine

Dept. Of AnatomyDept. Of Anatomy

Objectives:

At the end of this lecture we should be able to know :

1.The boundaries, roof, floor & contents of Anterior triangle

2.The boundaries, contents of posterior triangle

3.The role of Sternomastoid muscle in main anatomical division of the neck.

4.What are the careful and careless area of posterior triangle

5.What are the importance of diagastric and omohyoid muscles as a land marks for subdivision of the two triangular regions of neck.

Posterior trianglePosterior triangle

A. Posterior triangle

Is bounded by : posterior border of sternocleidomastoid muscle, anterior border of trapezius muscle, superior border of clavicle.

roof ………formed by :• platysma • investing (superficial) layer of deep cervical fascia.

floor :…….formed by : splenius capitis levator scapulae muscles anterior, middle, posterior scalene scalene muscles.

Sternocleidomastoid

Trapezius

Posterior cervical trianglePosterior cervical triangle

Is divided into :……. by omohyoid posterior belly

I. occipital triangle.

II. subclavian (supraclavicular) triangle.

Contains:

1.accessory nerve,

2.cutaneous branches of cervical plexus,

3.external jugular vein,

4.transverse cervical

5.suprascapular vessels,

6.subclavian vein & artery,

7.Inferior belly of omohyoid,

8.roots and trunks of brachial plexus.

9.nerve to subclavius

10.dorsal scapular,

11.suprascapular,

12.long thoracic nerves.

Triangles of posterior (lateral) region of neck

Triangles of posterior (lateral) region of neck

trapezius muscle

Sternomastoid muscle

Triangles of posterior (lateral) region of neck

clavicle

Sternomastoid muscle

Triangles of posterior (lateral) region of neck

Occipital trianglesupraclavicular triangle

(greater supraclavicular fossa)

Triangles of posterior (lateral) region of neck

Occipital trianglesupraclavicular triangle

(greater supraclavicular fossa)

Sternomastoid muscle

Sternomastoid muscle

trapezius muscle

Sternomastoid muscle

trapezius muscle

clavicle

Omohyoidmuscle Sternomastoid

muscle

trapezius muscle

clavicle

Scalenus anterior muscle

Sternomastoid muscle

trapezius muscle

clavicle

Omohyoidmuscle

Scalenus medius muscle

Sternomastoid muscle

trapezius muscle

clavicle

Omohyoidmuscle

Sterno thyroid m

Sternomastoid muscle

trapezius muscle

clavicle

Omohyoidmuscle

thyrohyoid m

Sternomastoid muscle

trapezius muscle

clavicle

Omohyoidmuscle

Sternohyoid m

Sternomastoid muscle

trapezius muscle

clavicle

Omohyoidmuscle

apex

trapeziusmuscle

Investing layer of deep fascia roof

Sternomastoid muscle

Middle 1/3 of clavicle – base

Nerves in posterior triangle

1-Cervical plexus

2-Brachial plexus

3 -spinal root of accessory

nerve (11th cranial nerve )

1 -four muscular branches

2 -four cutaneous branches

Roots , trunks and their branches

1 -dorsal scapular nerve –c5(nerve to

rhomboids )2 -nerve to subclavius

– c5 &c63 -nerve to serratus

anterior –c5,6 &7Suprascapular nerve –

c5&6

It is the most important

structure in the occipital triangle

Spinal part of accessory nerve

Platysma

Cutaneous nerves and superficial veins

External jugular vein

Anterior jugular vein

Lesser occipital n.

Greet auricular n.Transverse nerve of neck

Supraclavicular n.

Anterior triangleAnterior triangle

Anterior trianglesAnterior triangles

Prevertebral muscles

Scalene muscles

Suprahyoidmuscles

Infrrahyoidmuscles

B. Anterior triangleIs bounded by:

anterior border of sternocleidomastoid, anterior midline of neck, inferior border of mandible.

roof :……formed by:

•platysma

•investing layer of deep cervical fascia.

Is further divided by : omohyoidomohyoid superior belly digastric anterior and posterior bellies

into :

digastric (submandibular), submental (suprahyoid), carotid, muscular (inferior carotid) triangles.

Omohyoidmuscle Sternomastoid

muscle

Omohyoidmuscle Sternomastoid

muscle

Omohyoidmuscle Sternomastoid

muscle

Omohyoidmuscle Sternomastoid

muscle

apex

trapeziusmuscle

Investing layer of deep fascia roof

Sternomastoid muscle

Middle 1/3 of clavicle – base

Anterior trianglesAnterior triangles

Prevertebral musclesScalene muscles

Suprahyoidmuscles

Infrrahyoidmuscles

Anterior belly of digastric muscle

Posterior belly of digastric

Stylohyoid

Sternohyoid muscle

Digastric triangle

Above …………….lower border of mandible Below & infront …..anterior belly of Digastric muscle

Below & behind …..posterior belly of Digastric & stylohyoid muscles .

Floor : Floor : Anteriorly : ……..mylohyoidmylohyoid muscle Posteriorly ………part of hyoglossus part of hyoglossus muscle

Contents of Digastric triangle

submandibular salivary gland

submandibular lymph nodes lie on the surface of the gland

facial artery deep to posterior end of submandibular salivary gland

facial vein lies superficial to submandibular salivary gland

hypoglossal nerve

nerve to mylohyoid muscle

• dDigastric triangle

Anterior belly of digastric

Posterior belly of digastric

Mylohyoid muscle forms the floor of the mouth

Hyoid bone

C. Hyoid bone……..Is a U-shaped bone

consisting of : a median body, a median body, lesser horns (cornua) laterally, …………. paired lesser horns (cornua) laterally, …………. paired greater horns (cornua) posteriorly……… paired greater horns (cornua) posteriorly……… paired

1. Body

Provides for attachments for : Geniohyoid Geniohyoid musclemuscle, , mylohyoid, mylohyoid, musclemuscle

Omohyoid Omohyoid musclemuscle, , sternohyoid sternohyoid musclemuscle..

2. Greater horn

Provides attachments for : middle constrictor, middle constrictor, hyoglossus, hyoglossus, digastric (anterior and posterior) bellies, digastric (anterior and posterior) bellies, stylohyoid, stylohyoid, thyrohyoid muscle.thyrohyoid muscle.

3. Lesser horn

Provides attachment for :•stylohyoid ligamentstylohyoid ligament,

which runs from styloid process styloid process to lesser horn

Styloid process

D. Styloid process Is a slender projection of variable length extends downward & forward from temporal bonetemporal bone.

Gives origin to :three muscles:

stylohyoid, stylohyoid, styloglossus, styloglossus, StylopharyngeusStylopharyngeus

two ligaments :• stylohyoid stylohyoid • stylomandibular.stylomandibular.

Carotid triangle

boundary :

•Behind : …………..sternomastoidsternomastoid muscle

•Infront & above : posteriorposterior belly of digastricbelly of digastric muscle

•Infront&below : superior belly of omohyoidsuperior belly of omohyoid muscle

Floor : infont : hyoglossus muscle ( above ) and the thyrohyoid muscle (below)

•Behind: the middle constrictor muscle of the pharynx (above ) and the inferior constrictor muscle of the pharynx (below )

• d

Carotid triangle

Posterior belly of digastric

apex

trapeziusmuscle

Investing layer of deep fascia roof

Sternomastoid muscle

Middle 1/3 of clavicle – base

External carotid artery

Common carotid artery

Internal carotid artery

Contents of the Carotid triangle

• 1- The carotid sheath and its contents :

• - common carotid artery : in the lower part of the triangle .

• - internal carotid artery : in the upper part of the triangle .

• Internal jugular vein : lateral

• Vagus nerve : between the artery and the vein but in a more posterior plane .

• 2- the external carotid artery : gives most of its branches in the carotid triangle ( superior thyroid artery ,lingual artery ,facial artery , ascending pharyngeal artery and occipital artery )

• 3- hypoglossal nerve • 4- Descendes cervicalis (C2,3) anterior to

carotid sheath.• 5- sympathetic trunk adherent to the posterior

wall of carotid sheath

Contents of the Muscular triangle

• It contains the infrahyoid muscle

Contents of the Submental triangle

• 1- submental lymph nodes

• 2- beginning of the anterior jugular vein

The infrahyoid muscles

• They are strap like muscles occupy each side of the midline of the neck , from the hyoid bone to the manubrium sterni .

• They consist of 4 muscles arranged into 2 layers :

• 1- superficial layer : a- sternohyoid • B- omohyoid • 2- deep layer: a- sternothyroid • B- thyrohyoid

Suprahyoid muscles

• 1- digastric muscle

• 2- mylohyoid muscle

• 3- hyoglossus muscle

• 4- geniohyoid muscle

• 5- stylohyoid muscle

Geniohyoid muscle

Hyoglossus

Submendibular gland

OmohyoidSternohyoid

Sternothyroid

Superior thyroid a.

Cervical plexus

Phrenic n.

Ansa cervicalis

Vagus n.

Hypoglossal n.

Accessory n.Digastric

III. NervesIII. Nerves

A. Accessory nerve

Is formed by union of :• cranial &• spinal roots.

Has both spinal and cranial portions,

traverse jugular foramenjugular foramen,

they interchange fibers.

cranial roots :cranial roots :• arise from medulla oblongata below roots of vagusvagus.

spinal roots :spinal roots : arise from lateral aspect of cervical segment of spinal cord

between C1 – C5

unites to form a trunk ascends between dorsal & ventral roots of spinal nerves in vertebral canal passes through foramen magnumforamen magnum.

cranial portion contains motor fibers .. join vagus nerve innervate soft palatesoft palate, pharyngeal constrictorspharyngeal constrictors, & larynxarynx.

spinal portionspinal portion innervates sternocleidomastoid & trapezius muscles.Lies on levator scapulae in posterior cervical triangle passes deep to trapeziustrapezius.

B. Cervical plexusIs formed by ventral primary rami of C1 to C4.

1. Cutaneous branches1. Cutaneous branches

a- Lesser occipital nerve (C2)a- Lesser occipital nerve (C2)

• Ascends along posterior border of sternocleidomastoid to scalp

• behind auricle.

b- Great auricular nerve b- Great auricular nerve (C2-C3)

• Ascends on sternocleidomastoid

• innervate skin behind auricle & on parotid gland.

C- Transverse cervical C- Transverse cervical nerve (C2-C3)

• Turns around posterior border of sternocleidomastoid

• innervates skin of anterior cervical triangle.

D-SupraclavicularD-Supraclavicular nerve (C3-C4)

Emerges as a common trunk from under sternocleidomastoid

divides into anterior, middle, & lateral branches to skin over clavicle &shoulder.

2. Motor branches2. Motor branches

Ansa cervicalis………………Is a nerve looploop formed by union of :

superior root (C1) descendens hypoglossi

inferior root (C2--C3; descendens cervicalis.

Lies superficial to carotid sheath in anterior cervical triangle.

Innervates infrahyoid (strap) muscles:omohyoid, sternohyoid, sternothyroid muscles,

with exception of thyrohyoid musclethyrohyoid muscle, innervated by C1 C1 via hypoglossalhypoglossal nerve.

Phrenic nerve (C3-C5)Phrenic nerve (C3-C5)

Arises from chiefly from 4th4th cervical nerve;

contains : motor, motor, sensory, sensory, sympathetic nerve fibers; sympathetic nerve fibers;

Provides: motor supply to diaphragm sensation to its central part.

•Descends on anterior surface of anterior scalene anterior scalene muscle • under cover of sternocleidomastoid muscle.

•Passes between subclavian artery subclavian artery & veinvein at root of neck

•enters thorax by crossing in front of origin of internal thoracic arteryinternal thoracic artery, • it joins pericardiacophrenic branch of this artery.

•Passes anterior to root of lung • between mediastinal pleura & fibrous pericardium • supply sensory fibers to these structures.

longus capitis and cervicis or colli,

sternocleidomastoid,

trapezius,

levator scapulae,

scalene muscles.

Accessory phrenic nerve (C5)Accessory phrenic nerve (C5) arises as a contribution of :

C5 to phrenic nerve or a branch of nerve to subclavius (C5),

descends lateral to phrenic nerve, enters thorax by passing posterior to subclavian vein, joins phrenic nerve below first rib to supply diaphragm.

C. Brachial plexus

Is formed by union of Is formed by union of ventral primary rami ventral primary rami of C5 to T1 of C5 to T1 passes between anterior scalene & middle scalene musclespasses between anterior scalene & middle scalene muscles..

1. roots roots give rise to :

Dorsal scapular nerve (C5)o Emerges from behind anterior scalene anterior scalene muscle o runs downward and backward through middle scalene middle scalene muscle o deep to trapezius.o Passes deep to levator scapulae levator scapulae o descends along with dorsal scapular artery on deep surface of rhomboid muscles rhomboid muscles

along medial border of scapula,

Innervating:

levator scapulae levator scapulae rhomboid muscle.rhomboid muscle.

Long thoracic nerve (C5--C7) Pierces middle scalene middle scalene muscle, descends behind brachial plexus, enters axilla

innervate ……..serratus anteriorserratus anterior.

C. Brachial plexus

2. Iupper trunk Iupper trunk gives rise to :

Suprascapular nerve (C5-C6) Passes deep to trapezius joins suprascapular artery in a course toward shoulder. Passes through scapular notch under transverse scapular ligamenttransverse scapular ligament.

Supplies :

• supraspinatus supraspinatus

• infraspinatus musclesinfraspinatus muscles

Nerve to subclavius muscle (C5) Descends in front of plexus and behind clavicle innervate subclavius. Communicates with phrenic nerve as accessory phrenic nerve

Omohyoidmuscle Sternomastoid

muscle

apex

trapeziusmuscle

Investing layer of deep fascia roof

Sternomastoid muscle

Middle 1/3 of clavicle – base

Anterior belly of digastric muscle

Posterior belly of digastric

Stylohyoid

Sternohyoid muscle