Anatomy of the Head and Neck and Embryology

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ANATOMY OF THE HEAD AND NECK AND EMBRYOLOGY CRANIAL CAVITY The dura mater lines the inner aspect of the skull cap and the cranial cavity. It protects the brain from shock and friction with the hard skull. The dura is composed of 2 layers: 1. Outer layer. 2. Inner layer The 2 layers are closely adherent to each other. They are separated to form the venous dural sinuses. Dural venous sinuses are: -Valveless veins -Receive venous blood from the orbit, brain and adjacent bones - Present between the two layers of the dura The inner layer of the dura forms 4 folds inside the cranial cavity. The folds of dura mater are: 1. Falx cerebri A sickle-shaped fold, lies between the 2 cerebral hemispheres. Attachments: Anterior: crista galli. Posterior: upper surface of tentorium cerebelli. Superior: to the lips of the sagittal sulcus on the inner aspect of the skull cap. 1

Transcript of Anatomy of the Head and Neck and Embryology

Page 1: Anatomy of the Head and Neck and Embryology

ANATOMY OF THE HEAD AND NECK AND EMBRYOLOGY

CRANIAL CAVITYThe dura mater lines the inner aspect of the skull cap and the cranial cavity. It protects the brain from shock and friction with the hard skull. The dura is composed of 2 layers:1. Outer layer.2. Inner layer

The 2 layers are closely adherent to each other. They are separated to form the venous dural sinuses. Dural venous sinuses are:-Valveless veins -Receive venous blood from the orbit, brain and adjacent bones - Present between the two layers of the dura The inner layer of the dura forms 4 folds inside the cranial cavity. The folds of dura mater are:

1. Falx cerebriA sickle-shaped fold, lies between the 2 cerebral hemispheres.

Attachments: Anterior: crista galli. Posterior: upper surface of tentorium cerebelli. Superior: to the lips of the sagittal sulcus on the inner aspect of the skull cap.

Venous sinuses related to it:1. Superior sagittal sinus in its upper attached border.2. Inferior sagittal sinus in its free concave lower border.3. Straight sinus in the attachment of the falx cerebri with the tentorium cerebelli.

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Folds of the dura mater and the dural svenous sinuses

2. Tentorium cerebelliA tent-like fold over the cerebellum.

Attachment: The attached margin (peripheral) is attached to the posterior clinoid process, upper border of petrous temporal bone and to the margin of the groove for transverse sinus. The free margin: forms the tentorial notch around the midbrain and is attached anteriorly to the anterior clinoid process. This margin crosses the attached one at the petrous apex. The trochlear nerve pierces the dura at the point of crossing, while the oculomotor nerve pierces the dura in front of crossing point. The upper surface gives attachment to the falx cerebri.

Venous sinuses related to tentorium: Straight sinus (between the attachment of the falx cerebri and the supper surface of tentorium). Superior petrosal sinus in the attached margin. Transverse sinus in the attached margin.

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3. Falx cerebelliA small crescentic fold between the 2 cerebellar hemispheres.

Attachment: To the internal occipital crest.

Venous sinuses related: Occipital sinus.

4. Diaphragma sellaeIt is a dural fold covering the pituitary gland located in the

hypophyseal fossa. It is pierced by the pituitary stalk. It is attached to the anterior and posterior clinoid processes.

Venous sinuses related:Anterior: Intercavernous sinus.Posterior: Intercavernous sinus.

Cranial Venous sinuses

A- Single B- Paired1. Superior sagittal.2. Inferior sagittal.3. Straight sinus.4. intercavernous.5. Occipital.6. Basilar plexus of sinuses.

1. Spheno-parietal.2. Cavernous.3. Superior petrosal.4. Inferior petrosal.5. Transverse sinus.6. Sigmoid sinus

Superior Sagittal Sinus It begins at the apex of falx cerebri above the crista galli and ends a little to the right of the internal occipital protuberance by turning to the right side and becoming the right transverse sinus. It may open into a dilatation called confluence of sinuses at the internal occipital protuberance.

Inferior Sagittal SinusIt runs along the posterior half or two-thirds of the free margin of the falx cerebri. It is of a cylindrical form, increases in size as it passes backward, and ends at the free margin of tentorium by uniting with the great cerebral vein to form the straight sinus.

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Straight Sinus It is situated at the line of junction of the falx cerebri with the tentorium cerebelli.It is formed by the union of the inferior sagittal sinus and great cerebral vein. It terminates at the internal occipital protuberance by forming the left transverse sinus. It may open in the confluence of sinuses.

Transverse Sinus It begins at the internal occipital protuberance as follows:- The right sinus is usually the continuation of the sup. sagittal sinus.- The left sinus is usually the continuation of the straight sinus.

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Sigmoid Sinus It begins as a continuation of the transverse sinus. It ends by passing through the posterior compartment of the jugular foramen to become the internal jugular vein

Intercavernous Sinuses They are two in number, an anterior and a posterior, and connect the two cavernous sinuses across the middle line.◦ The anterior passes in front of the hypophysis cerebri.◦ the posterior behind it◦ they form with the cavernous sinuses a venous circle (circular sinus) around the hypophysis.

Occipital Sinus It is the smallest of the cranial sinuses. It is situated in the attached margin of the falx cerebelli, and is generally single, but occasionally there are two, Rt. and Lt. arising from Rt. and Lt. Transverse sinuses. they fuse together to form a single sinus which ends into the sigmoid sinus in each side. It commences around the margin of the foramen magnum by several small meningeal veins.Cavernous sinusPosition: on each side of sphenoid bone in the cranial cavity. It extends from the superior orbital fissure anteriorly to the apex of petrous bone posteriorly.

Relations: Roof: Base of the brain, diaphragm sellae, and internal carotid artery. Floor: Body of sphenoid and sphenoid air sinus. Medially: Pituitary gland, body of sphenoid bone, and sphenoid air sinus. Laterally: Uncus of temporal lobe of the brain, and the trigeminal ganglion.

Contents: - In the lateral wall (from above downward): Oculomotor (III), trochlear (IV), ophthalmic (V1), and Maxillary (V2) nerves. - In the floor: ICA, and abducent (VI) nerve.Tributaries:1. Superior ophthalmic vein.2. Inferior ophthalmic vein3. Central vein of the retina.4. Spheno-parietal sinus.

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5. Superficial middle cerebral vein.

Communications:1. With the facial vein through the superior ophthalmic vein.2. With the opposite side through intercavernous communications.3. With the pterygoid and pharyngeal plexus of veins through emissary veins passing through foramen ovale and lacerum.

Drainage:1. To the superior petrosal sinus to end in the transverse sinus.2. To the inferior petrosal sinus to end in the internal jugular vein.

Applied anatomy:Infection of the cavernous sinus (cavernous sinus thrombosis) may

be fatal. It could be transmitted to:1. The brain through the superficial middle cerebral vein.2. Eye ball (leading to oedema of the eye ball and lids).3. It leads to affection of the cranial nerves related to the cavernous sinus leading to squint (due to nerve irritation) or ophthalmoplegia (due to complete nerve compression).4. It leads to affection of internal carotid artery causing pulsating exophthalamos.

Relations of cavernous sinus

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1, superior ophthalmic vein; 2, anterior intercavernous sinus; 3, inferior ophthalmic vein; 4, pterygoid plexus; 5, middle meningeal vein; 6, superior petrosal sinus; 7, inferior petrosal sinus; 8, basilar venous plexus; 9,transverse sinus; 10, posterior intercavernous sinus; 11, cavernous sinus; 12,sphenoparietal sinus

Tributaries, Communications, and drainage of cavernous sinus

SCALP

The skin of the scalp continues from the front and lateral side of the face into the occipital region of the skull posteriorly. The scalp is important clinically because trauma to the scalp is frequent and produces profuse bleeding.

The scalp is made up of 5 layers: S – Skin. C -- dense Connective tissue. It contains fat lobules, C.T. septa and many blood vessels (which bleeds profusely if injured. This layer is called the vascular layer. A – Aponeurosis (galea aponeurotica) and occipitofrontalis muscle. L -- Loose connective tissue. Bleeding in this layer is massive and my reach the eyelids causing blue eyes. P – Periosteum.

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Layers of the scalp

Blood supply of scalp:There are 5 arteries that supply the scalp:1. Supra orbital artery.2. Supra trochlear artery. These 2 arteries are branches from the ophthalmic artery which is a branch of the internal carotid artery.3. Superficial temporal artery.4. Posterior auricular artery.5. Occipital artery. The later 3 arteries are branches of the external carotid artery. This means that the scalp is an important site of anastomosis between the external and the internal carotid arteries. The first 3 arteries supply the area of the scalp in front of the auricle, while the last two arteries supply the area of the scalp behind the auricle.Nerve supply of scalp:I. MOTOR: The scalp contains a muscle which is the occipitofrontalis muscle. This muscle is supplied by the facial nerve (VII) by the temporal branch anteriorly and the posterior auricular branch posteriorly. II. SENSORY: The anterior part of the scalp (anterior to the auricle) is supplied by branches from the 3 divisions of the trigeminal nerve. The posterior part of the scalp (posterior to the auricle) is supplied by branches from cervical spinal nerves. There are 4 nerves anterior to the auricle and 4 nerves posterior to the auricle.

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- Anterior to the Auricle: Supratrochlear, supraorbital (ophthalmic V), zygomaticotemporal (maxillary V), and the auriculotemporal (mandibular V) nerves.- Posterior to the Auricle: Greater auricular, lesser occipital, 3rd occipital and greater occipital nerves.

Occipitofrontalis muscle is formed of occipital bellies and frontal bellies which are attached to the galea aponeurotica.

Sensation from scalp and face. Note that the anterior part of scalp is supplied by branches from the trigeminal nerve, while the posterior part is supplied by the cervical nerves

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FACE

Muscles of the face:Under the skin of the face there are more than 20 muscles that are attached to bone as well as to the skin. These muscles are called muscles of facial expression. The most important are the following 3 muscles:

Orbicularis oculi: It is a circular muscle around the eye opening. It is formed of an orbital part that covers the bone, lacrimal part, and a palpebral part that is present in the eyelid. Orbicularis oris: It is a circular muscle the surrounds the mouth opening. Buccinator: It is the muscle of the check. It is pierced by the duct of the parotid gland.All the muscles of the face are supplied by the “Facial Nerve” which is the cranial nerve (VII).

Muscles of the face. The muscle surrounding the eye opening is the orbicularis oculi. The muscle surrounding the opening of the mouth is the orbicularis oris. The muscle of the check is the buccinator

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Arteries of the face: Facial Artery Transverse Facial artery Infraorbital artery Mental artery Supraorbital and supratrochlear arteries Superficial temporal artery

Arteries supplying the face

Veins of the face:

The face is drained by the anterior facial vein (facial vein) and the posterior facial vein (retromandibular vein). The anterior facial vein (facial vein) commences at the medial angle of the eye as a direct continuation of the angular vein. It lies behind the facial artery and follows a less tortuous course. It usually joins the anterior branch of the posterior facial (retromandibular) vein to form the common facial vein that drains into the internal jugular vein.

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The retromandibular vein (posterior facial vein) begins behind the neck of mandible by union of the superficial temporal and the maxillary veins. This happens inside the substance of the parotid gland. It passes downwards and divides into anterior and posterior branches. The anterior branch unites with the anterior facial vein to form the common facial vein that finally drains into the internal jugular vein. The posterior branch of retromandibular vein unites with the posterior auricular vein to form the external jugular vein (superficial to the sternomastoid muscle).

Veins of the face.

Nerve supply of the face:I. MOTOR:All the muscles of the face are supplied by the Facial Nerve which is the 7th cranial nerve. The facial nerve leaves the skull by passing through the stylomastoid foramen and then curves anteriorly to enter inside the

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parotid gland, where it divides into its 5 terminal branches that supply the muscles of the face. The terminal branches of the facial nerve are: 1. Temporal.2. Zygomatic.3. Buccal. 4. Mandibular.5. Cervical.

II. SENSORY:The sensation from the skin of the face is carried by the TRIGEMINAL (Vth cranial) NERVE.The trigeminal nerve divides in the cranial cavity into 3 divisions: Ophthalmic, Maxillary, and Mandibular

Summary of the motor and sensory nerve supply of the face.The muscles of the face are supplied by the five terminal branches of the facial nerve. The sensory supply is by the three divisions of the trigeminal nerve.

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TRIANGLES OF THE NECKThe side of the neck is divided by the sternomastoid muscle into:1. Anterior triangle in front of the muscle.2. Posterior triangle behind the muscle.

POSTERIOR TRIANGLE OF THE NECK

Boundaries: Anterior: Posterior border of the sternomastoid muscle. Posterior: Trapezius muscle. Roof: The investing layer of deep cervical fascia. Floor: Is formed of the following muscles covered with prevertebral fascia: (muscles are arranged from below upward)1. Scalenus medius.2. Levator scapulae.3. Splenius capitis.4. Semispinalis capitis.Apex: at the superior nuchal line.Base: middle third of the clavicle.

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Triangles of the neck

Contents:1. Arteries:a. Subclavian artery (3rd part).b. Suprascapular artery.c. Transverse cervical artery.Notice that the suprascapular and the transverse cervical arteries are branches from the thyrocervical trunk of the first part of subclavian artery.2. Veins:a. Subclavian vein.b. External jugular vein.3. Nerves:a. Roots and trunks of the brachial plexus. b. Spinal part of accessory nerve.c. Cutaneous branches of the cervical plexus.4. Muscles: Inferior belly of omohyiod muscle.5. Lymph node: Occipital and supraclavicular lymph node.

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The sternomastoid muscle divides the neck into anterior and posterior triangles

ANTERIOR TRIANGLE OF THE NECKBoundaries:Anteriorly: Midline of the neck.Posteriorly: Anterior border of sternomastoid muscle.Base: Formed by the lower border of the mandible.

Subdivisions of the anterior triangle:1. Submental triangle.2. Digastric triangle.3. Carotid triangle.4. Muscular triangle.

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Floor and contents of the posterior triangles

Submental triangleBoundaries:1. Anterior belly of right digastric muscle.2. Anterior belly of left digastric muscle.3. Hyoid bone inferiorly.Floor: is formed by the 2 mylohyoid muscles & their raphe.Contents:1. Submandibular lymph nodes.2. Submental veins.3. Submental branch of facial artery.4. nerve to mylohyoid.

Carotid triangleBoundaries:- Anterior border of sternomastoid.- Posterior belly of digastric muscle.- Superior belly of omohyoid. Floor:- Formed by hyoglossus, thyrohyoid, middle and inferior constrictors of the pharynx.Contents:1. Carotid sheath and its content.2. External carotid artery.

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3. Sympathetic trunk.4. Upper and lower deep cervical lymph nodes.5. last three cranial nerves (X, XI, XII).6. Ansa cervicalis.

Subdivisions of the anterior triangle of the neck

Digastric triangleBoundaries:- Lower border of the mandible.- Anterior and posterior bellies of digastric muscle.Floor: Formed by mylohyoid and hyoglossus muscles.Contents:- Submandibular salivary gland.- Submandibular lymph node.- Facial artery and anterior facial vein.- hypoglossal nerve and nerve to mylohyoid

Muscular triangleBoundaries:- Superior belly of omohyoid.- Anterior border of sternomastoid.- Midline of the neck.Contents: Infrahyoid muscles.

- The infrahyoid muscles are arranged in 2 layers:

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1. The superficial layer is formed of the superior belly of omohyoid laterally and sternohyoid muscle medially.2. Deep layer formed of thyrohyoid & sternothyroid muscles. - All the infrahyoid muscles are supplied by ansa cervicalis except thyrohyoid (supplied by C1 only).

Infrahyoid and suprahyoid muscles

LAST FOUR CRANIAL NERVES

Glossopharyngeal nerve (IX)It is the ninth cranial nerve.Origin: from the medulla oblongata.Course and relations:It leaves the skull by passing through the jugular foramen, deep to the styloid process and styloid apparatus.It lies between the internal and the external carotid arteries. It runs on the stylopharyngeus. It passes between the superior and middle constrictors of the pharynx. It lies on the medial (deep) surface of hyoglossus muscle. It ends in the posterior third of the tongue.Branches:1. Tympanic branch forming lesser superficial petrosal nerve. It carries secretomotor fibers to the parotid gland.2. Tonsillar branch supplying the palatine tonsil.3. Muscular branch to supply stylopharyngeus.

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4. Lingual branch carrying taste and general sensations to the post third of the tongue.5. Pharyngeal branch to share in the pharyngeal plexus.

Branches of Glossopharengeal Nerve

Vagus Nerve (X)

It's the tenth cranial nerve.Course & relations: It leaves the posterior cranial fossa through the jugular foramen. It descends in the neck within the carotid sheath between the internal jugular vein and the internal carotid artery. At the level of upper border of thyroid cartilage it lies between the internal jugular vein and the common carotid artery in the carotid sheath. It enters the thorax by crossing the 1st part of subclavian artery.

Branches:1. Meningeal branch.2. Auricular branch to the skin of the external auditory meatus.3. Pharyngeal branch.4. Recurrent laryngeal nerve supplies : - The mucosa of the larynx above the vocal folds.

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- All intrinsic muscles of larynx except the cricothyroid muscle (supplied by external laryngeal nerve).- The right recurrent laryngeal nerve originates from the right vagus nerve in the neck, while the left recurrent laryngeal nerve originates from the left vagus in the thorax. 5. Superior and inferior cardiac branches.6. Superior laryngeal nerve:It divides into external and internal laryngeal nerves. The internal laryngeal nerve pierces the thyrohyoid membrane to supply the mucosa of the larynx above the vocal folds. The external laryngeal nerve supplies the cricothyroid muscle.

Branches of the Vagus NerveAccessory Nerve (XI)

It’s the eleventh cranial nerve.Parts and origin:It has 2 parts arises from different origins:a) Cranial part: arises from the medulla oblongata of the brain stem.b) Cervical part: arises from the upper 5 cervical segments of the spinal cord.

Course & relations:Spinal part: - Ascends to enter the cranial cavity by passing through the foramen magnum. It joins the cranial part. After joining, the two parts of the accessory nerve pass through the jugular foramen. - Below the jugular foramen, the accessory nerve divides into

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its 2 original parts (spinal & cranial).- The spinal part descends alone deep to the styloid process. - It pierces the sternomastoid muscle to supply it.- It crosses the posterior triangle.- Then, it passes deep to trapezius muscle supplying it.Cranial part:- It leaves the cranial cavity through the jugular foramen after joining the spinal part.- Below the skull it separates from the spinal part.- The cranial part then joins the vagus and is distributed through its pharyngeal and laryngeal branches.

Distribution:1. Cranial part: together with the vagus nerve, they supply: - All muscles of palate except tensor palate (supplied by mandibular nerve). - All muscles of pharynx except the stylopharyngeus (supplied by glossopharyngeal

nerve). - All the intrinsic muscles of larynx.

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2. Spinal part:It supplies the following muscles: - Sternomastoid. - Trapezius.

Origin and branches of Accessory nerve

Hypoglossal Nerve (XII)

It is a pure motor nerve.Origin: - It arises from the medulla oblongata of the brain stem.Course & relations:- It leaves the skull through the hypoglossal canal. It lies deep to the carotid sheath and the structures that pass from the jugular foramen (gloss- pharyngeal, vagus and accessory nerves). - It passes deep to posterior belly of digastric and stylohyoid muscles. It crosses the internal carotid artery, external carotid arteries and the loop of lingual artery superficially. - It passes lateral to hyoglossus muscle, along the upper border of hyoid bone, deep to the submandibular gland. It breaks into terminal branches to supply the muscles of tongue.

Branches:1. It gives muscular branches to all the muscles of tongue ,except the palatoglossus (supplied by the cranial accessory nerve through branches of the vagus nerves).2. By carrying the C1 it supplies the thyrohyoid & geniohyoid muscles.

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Hypoglossal Nerve and Ansa Cervicalis

Ansa cervicalisIt is formed by:1. superior root formed of C1, it is carried by the hypoglossal nerve.2. inferior root formed by C2 & 3.The superior and inferior roots join each other forming a loop anterior to the carotid sheath.Branches:1. Pure C1 supplies the thyrohyoid & geniohyoid muscles.2. C1, 2 & 3 supply all the infrahyoid muscles except the thyrohyoid muscle.

Branches of Ansa Cervicalis

THE LYMPHATIC DRAINAGE OF HEAD AND NECK Lymph nodes of the head and neck are arranged into:1- Superficial group.2- Deep group.- Each group contains transverse and vertical (mid line & 2 lateral) groups of lymph nodes.- All the superficial system drains into the deep system. Efferents of deep cervical lymph nodes drain into the jugular lymph trunk which drains into:

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A- on the right side right lymphatic duct. B- on the left side into the thoracic duct. Both the right lymphatic duct and thoracic duct drain into the junction of subclavian and internal jugular veins on their own side.

Deep cervical lymph nodes- It is formed of:- Vertical group: lies along the internal jugular vein.- Transverse group.

The vertical group is formed of: 1 – Upper deep cervical lymph nodes: - Along the upper part of internal jugular vein. Most of them lie deep to sternomastoid and few extend beyond it. - Ex: jugulo-digastric lymph nodes.2 – lower deep cervical lymph nodes:- Are partly deep to the lower part of sternomastoid. Related to brachial plexus and subclavian vessels.Ex: jugulo-omohyoid lymph nodes.

Lymph nodes of the head and neckJugulo omohyoid lymph nodes

Jugulo digastric lymph nodesName of LN

Above the intermediate tendon of omohyoid.Posterior to internal jugular vein.

Behind the posterior belly of digastric muscle.In front of internal jugular vein.

Site

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1 .Submental.2 .Submandibular (Submaxillary)

Anterior Cervical Lymph Nodes (Deep)3 .Prelaryngeal.

4 .Thyroid.5 .Pretracheal.

6 .Paratracheal.

Deep Cervical Lymph Nodes.7 .Lateral jugular.

8 .Anterior jugular.9 .Jugulo-digastric.

Inferior Deep Cervical Lymph Nodes10 .Jugulo-omohyoid

11 .Supraclavicular (scalene).

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1- anterior part of tongue.2 – anterior part of scalp.3 – lower part of pharynx and larynx.4 – thyroid gland.

1- back of tongue.2 – tonsils, ear and sinuses.3 – upper part of the pharynx.

Tributaries

From lower deep cervical lymph nodes to join the jugular trunk.

From the upper deep cervical lymph nodes to lower deepCervical lymph and direct to jugular trunk.

Drainage

The transverse group:- It forms a ring called Waldeyer's ring. This ring is formed of:1. Pharyngeal tonsil (adenoid).2. Tubal tonsil (around the pharyngeal opening of the auditory tube in the nasopharynx).3. Palatine tonsil.4. Lingual tonsil in the posterior third of the tongue.

The superficial lymph nodes of the head and neck- It is composed of transverse and vertical groups.

- The transverse group forms a ring. This ring is made by:

1. Occipital lymph nodes Site : at the upper angle of posterior triangle.Afferent : occipital region of scalp.Efferent : to lower deep cervical lymph nodes. 2. Postauricular lymph nodes ( mastoid nodes) Site : superficial to the lateral surface of mastoid process and deep to the auricularis posterior. Afferent: auricle, floor of meatus, skin over angle of jaw, and lower part of the parotid region.Efferent: to the upper deep cervical lymph nodes.

3- Parotid lymph nodes (periauricular)Site: embedded in the parotid salivary gland. Afferent: middle ear, medial part of the upper eyelid, and the medial half of lower lid.Efferent: terminate in submandibular group of lymph node.

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The superficial lymph nodes of the head and neck

4- The submandibular lymph nodesSite: are internal to deep cervical fascia in the sub mandibular region. Afferent: vessels from submental, buccal and lingual lymph nodes.Efferent: pass to upper and lower cervical lymph nodes.

5- Submental lymph nodes Site: present on the mylohyoid between anterior bellies of the two digastric muscles.Afferent:- Floor of mouth and tip of tongue.- Both side of median plane. Efferent: - The submandibular and jugulo-omohyoid nodes. N.B

The vertical group of superficial lymph nodes forms of two vertical columns: 1. A mid line vertical column lies along the anterior jugular vein.2. A vertical lateral column along the external jugular vein in the posterior triangle and superficial to the sternomastoid muscle.

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The lymphatic drainage of the upper part of the anterior triangle of the neck is drained into submandibular, submental nodes.

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Lymphatic drainage of the deep structures of head and neck The deep structures of the head and neck drain to the deep cervical lymph nodes either directly or indirectly by:

1- The retero pharyngeal lymph nodes It comprises a median and two lateral groups. The former lies near the midline, the latter in front of lateral mass of the atlas along the lateral border of longus capitis. Site: They lie between the fascia covering the pharynx and the prevertebral fascia. Afferent: From nasopharynx, the auditory tube, the atlanto–occipital and atlanto axial joint. Efferent: To upper deep cervical lymph nodes. 2- The paratracheal lymph nodesSite: flank the trachea and oesophagus. Afferent: The cervical part of the trachea and the thyroid gland.Efferent: Pass to deep cervical nodes.

Superficial and deep lymph nodes of the head and neck

Lymphatic drainage of the nasal cavity, nasopharynx and middle ear - The anterior part of nasal cavity drain to submandibular nodes.

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- The remainder of nasal cavity, Para nasal sinuses, nasopharynx and pharyngeal end of auditory tube drain to upper deep cervical nodes directly or through reteropharyngeal. - The posterior part of floor of nasal cavity is drained to parotid group of nodes. Lymphatic drainage of larynx1- Above the vocal cord drains into the upper deep cervical lymph nodes. 2- Below the vocal cord drains into the lower deep cervical lymph nodes.3- Few lymphatics pass to pretracheal and prelaryngeal then to deep cervical lymph nodes.

Lymphatic drainage of mouth, teeth tonsil and tongue

The mouth- Vessels of the gums end in the sub mandibular lymph nodes. - Hard palate end in the upper deep cervical nodes and retro pharyngeal lymph nodes.- The soft palate ends partly in upper cervical lymph node and retro pharyngeal lymph nodes.- The anterior part of the floor of mouth goes to inferior nodes of upper deep cervical group - The rest of the floor of the mouth goes to submandibular and upper deep cervical nodes.

The teeth: to sub mandible and deep cervical lymph nodes. The tonsil: most of them end in the jugular digastrics nodes.

The tongue: Anterior 2/3 of tongue Tip: sub mental nodes.Sides: sub mandible nodes.Central part: deep cervical lymph node.Posterior 1 /3 of tongue: deep cervical lymph nodes.

DEVELOPMENT OF CNSOrigin: EctodermDevelopment:At the 3rd week an ectodermal thickness (neural plate) appeared in the mid dorsal region cranial to the primitive node. The lateral edges of this plate called the neural folds. These folds elevate and approach each other in the mid line. They fuse together to form the neural tube. The neural tube is separated from the surface ectoderm. The fusion occurs at the 4th

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week; it starts in the cervical region and extends cranial and caudal. Once fusion is initiated the opened end of the neural tube form cranial and caudal neuropores which are communicated to the amniotic cavity.

Development of neural tube

The cranial portion of the neural tube shows 3 dilatations:-Prosencephalon (fore brain vesicle). At the 5th week it differentiates into central portion called diencephalon having the optic vesicle, and 2 lateral extensions called talencephalonMesencephalon (mid brain vesicle).Rhombencephalon (hind brain vesicle). Differentiates into metencephalon (future pons and cerebellum) and mylencephalon (future medulla oblongata)

2 flexures appear:1. Cephalic flexure: in the in the mid brain region2. Cervical flexure: at the junction between the hind brain and

spinnal cord

Later on another flexure called pontine flexure appears between the pons and myelenencephalon.

The neural canal (cavity of the neural tube):Cavity in the taloncephalon forms the lateral ventricleCavity in the diencephalon forms the 3rd ventricleCavity of the hind brain forms the 4th ventriclecavity in the spinal cord forms the central canal

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Brain vesicles

Neural crest cells:This is group of cells on either side of the neural plate. They are originated from ectoderm. They are found along the whole length of the neural tube. The cells of the neural crest migrate to form neural crest derivatives:Melanocytes.Suprarenal medulla.Neurolemmal sheath of peripheral nerves.Ganglion cell (sensory & sympathetic).Pia & arachniod matter.Odontoblasts. 7. Mesenchyme of the pharyngeal arches.

Branchial (pharyngeal) apparatus

The branchial apparatus consists of five branchial arches, four branchial grooves, four branchial pouches. It constitutes to the development of head and neck.The arch no. 5 degenerates. So, we have 1,2,3,4 and 6arches.

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Nerve supply of the arches

Arch Main nerve Small nerve

Maxillary process Maxillary nerve -------------------

Mandibular process

Mandibular nerve Chorda tympani of facial nerve

2nd arch Facial nerve (7th) Tympanic branch of glossopharyngeal nerve

3rd arch Glossopharyngeal nerve (9th) Internal laryngeal

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4th arch External laryngeal nerve

(11th)

--------------------

6th arch Recurrent laryngeal nerve

(11th )

--------------------

I Mesodermal Derivatives:

Arch Skeletal structures

Maxillary process *Squamus part of temporal bone

*zygomatic bone *Palatine bone*Maxilla

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Mandibular process (Mickel’s cartilage)

*Dorsal part------ Malleus +Incus Middle part----- Anterior ligament of malleus+ Sphenomandibular ligament*Ventral part---- Disappears (mandible devalops around it)

2ndarch (Reichert’s cartilage)

*Dorsal part------ Stapes + Styloid process*Middle part----- Stylohiod ligament*Ventral part----- Upper part of body of hyoid + lesser cornu of hyoid bone

3rd arch *Greater cornu + lower part of hyoid bone*Upper part of epiglottis

4tharch *Upper part of thyroid cartilage*Lower part of epiglottis

6tharch *Lower part of thyroid cartilage*Cricoid+ Arytenoid+ Corniculate+ cuneiform cartilage

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Arch Muscles

Maxillary process No

Mandibular process (Mickel’s cartilage)

*Four Muscles Of mastication*Tensor palati *Tensor tympeni *Mylohyoid *Anterior belly of digastric

2nd arch (Reichert’s cartilage)

*Muscles of face, scalp and auricle *Posterior belly of digastrics *Stapedius *Stylohyoid *Platysma

3rd arch *Stylopharyngeus

4th arch *Cricothyroid *Conistrictors of pharynx*Levator palati

6th arch *Intrinsic muscles of Larynx except cricothyroid muscle

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Derivatives:

Arch or Pouch Derivatives

!st Pouch *Middle ear and mastoid antrum*Auditory tube and inner layer of tympanic membrane

2nd Pouch *Palatine tonsil

3rd Pouch *Inferior parathyroid gland (Dorsal portion)*Thymus gland ( Ventral portion)

4th Pouch *Superior parathyroid gland ( Dorsal portion)*Ultimobranchial Body (Ventral portion)

III Ectodermal Derivatives:

Arch Derivatives

1st Arch *Epidermis of the skin covering the mandible and maxilla, lower lip and lateral part of upper lip*Enamel of teeth*Tragus of the ear

1st Cleft *External auditory meatus*Outer layer of tympanic membrane

2nd Arch *The caudal growth of the second archà Operculumà Epidermis of the skin of the side of the neck

3rd ,4th and

6th Arches

*They lie at the bottom of the cervical sinus and leave notraces

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Congenital Anomalies;1-External cervical sinus: Due to failure of obliteration of the cervical sinus. 2-Internal cervical sinus: It opens into the oropharynx. 3-Branchial cyst: Due to closure of the external opening leaving a space in the neck as a painless cyst. 4-Branchial fistula: A connection between the normal sinus and oropharynx forming a canal passing between the external and internal carotid arteries.

Development of the faceStages of development:1- Stage of processes: Five processes appear around the stomodium:(one frontonasal +two maxillary + two mandibular). 2- Stage of meeting. 3- Stage of fusion.

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Structures contributing to the formation of the face:

Face process and its derivatives

Stuctures Formed

Frontonasal Forehead- tip, dorsum and ala of nose- upper eye lids- philtrum of the upper lip.

Maxillary Upper lids- upper part of the cheeks- lateral part of the upper lip- upper jaw.

Mandibular Lower lip- chin- lower part of the cheeks- lower jaw.

Correlation between sensory nerve supply of the face and its development:

Face process and its derivatives Nerve supply

Fr Frontonasal Ophthalmic nerve

Maxillary Maxillary nerve

Mandibular Mandibular nerve

Congenital anomalies:1-Cleft upper lip (hare lip): Due to failure of fusion between maxillary and intermaxillary processes (philtrum and lateral part of upper lip) .2-Oblique facial cleft: Due to failure of fusion between maxillary process and lateral and medial nasal processes.3-Median cleft lower lip: Due to failure of fusion between the mandibular processes. 4-Macrostomia (large mouth): Due to arrest of fusion between the maxillary and mandibular processes to shift the angle medially >>> very big oral fissure.5-Microstomia: Due to excessive fusion between the maxillary and mandibular processes >>>>very small oral fissure.

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Development of the palateStages of development:1- Stage of processes: (primitive or primary palate + two palatine processes giving secondary palate). 2- Stage of meeting. 3- Stage of fusion. Intermaxillary processà 1ry palateà premaxilla of hard palateàIncisive fossa.Maxillary processes à palatine processesà 2ry palate à meeting& fusion with 1ry palate.The anterior ¾ of the palateà ossifyà hard palate & posterior ¼ à the soft palate.

Congenital anomalies:1- Cleft palate: a- Bifid uvula. b- Cleft soft palate. c- Cleft soft and hard palate.Due to failure of fusion between the processes.2- Perforated palate:

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due to failure of fusion between the two palatine processes at certain points.

Development of tongue:1- The anterior two thirds: Origin: The 1st Pharyngeal arch (mandibular processes)à two lateral lingual processes+ one tuberculum imparà meet à fuse à anterior 2/3 of the tongueà U shaped sulcusà mobile tongue leaving frenulum linguae.2- The pharyngeal part (posterior third): Origin: 2nd and 3rd pharyngeal archesà four swellings à meet à fuseà copula of Hisà posterior third of the tongue.N.B.: 1- The site of fusion between the lateral lingual swelling is indicated by the median sulcus.2- The site of fusin between anterior 2/3 & posterior 1/3 is indicated by Y- staped sulcus terminalis.

Development of the tongue (early)

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Development of the tongue (late)

Development of the tongue (final)

Muscles of the tongue:Three or four occipital myotomes migrate to enter the tongue forming muscles of the tongue.The occipital myotomes are supplied by the hypoglossal nerve which migrate with them to supply the tongue muscles during their development.Correlation between development of tongue and its nerve supply:

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Anterior 2/3 develop from the first arch à supplied by mandibular nerve and chorda tympani (nerves of 1st arch).Posterior 1/3 develops from the second and third arches but it is supplied by the glossopharyngeal nerve and internal laryngeal nerves( nerves of the third arch). This is because the element of the third arch grows superficially over the element of the second arch and hid it.Occipital myotomes are supplied by hypoglossal nerve which migrates with them to supply the tongue muscles.

Congenital anomalies:1- Bifid tongue: Due to incomplete fusion between the two lateral lingual swellings.2- Trifid tongue: The tuberculum impar elongates& separates the lateral swellings à three parts.3- Tie tongue ( ankyloglossia): due to attachment of frenulum linguae to the tip of the tongueà interfere with protrusion and speech.4- Macroglossia: large tongue.5- Microglossia: small tongue.6- Hemiglossia: Non development of one lateral swelling.7- Aglossia: no tongue.

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