30 Neck fascia and triangles

OPTIONAL READING

Moore, Clinically Oriented Anatomy, 7th ed., Fascia of neck section through Surface anatomy of cervical regions and triangles of neck.

Sur fa ce fe atures and l andm arks

The anterior neck (“neck proper” or cervix): extends from the inferior border of the mandible superiorly to the clavicles and sternum inferiorly.
The posterior neck (nucha or “nape”): extends from occipital bone and mastoid processes above to C-7 vertebra and the trapezius muscles below.
Hyoid Bone: in anterior midline located at ~C3; palpable floating “U shaped” bone
Good landmark for neck structures, and several cartilages of the larynx
Consists of a body, 2 greater horns, and 2 lesser horns
The hyoid does not articulate with other bones, instead, it attaches to many anterior neck muscles (suprahyoid and infrahyoid), and muscles of the larynx and pharynx.

Figure 30.1 GRAY’ S ANATOMY FOR STUDENTS, 3RD ED., FIGURE 8.157.

Muscles of the neck

We start with muscles because many of them are landmarks for neck structures!!

They are also used to define the triangles of the neck, described later in the chapter.

• Sternocleidomastoid muscle (SCM)

Major neck boundary, separating the anterior triangle from theposterior triangle
Origin: mastoid process and superior nuchal line
Insertion: sternal head: round tendon to manubrium; clavicular head:medial 1/3 of clavicle
Unilateral contraction produces lateral neck flexion and headrotated so the face is turned toward the opposite side (contraction of right SCM tilts and rotates the head to the left).
Bilateral contraction produces neck flexion (chin to thorax)
Innervation: CN XI

• Trapezius muscle

Attachments: superior nuchal line, external occipitalprotuberance, nuchal ligament, spinous processes C7–T12 and clavicle.
Elevates, retracts, and rotates the scapula superiorly (details are thelimb part of the course) – it is an important muscle for shoulder shrugging.
Posterior boundary of the posterior (neck) triangle
Innervation: CN XI

• Suprahyoid muscles

Attach the hyoid bone to the mandible and temporal bones; constitute the floor of the mouth; involved in elevating the hyoid bone during the first stages of swallowing; assist in opening the mouth
Muscles of suprahyoid region, with innervations:
Digastric: anterior and posterior bellies joined by a tendon that glides in a fibrous sling at the greater horn of the hyoid
Anterior belly: nerve to mylohyoid (from V3); posterior belly: Cranial nerve VII

• Mylohyoid (V₃: nerve to mylohyoid);

Stylohyoid (VII): splits around digastric tendon to attach to hyoid at the greater horn
Geniohyoid (C1 nerve fibers, by hitching a ride on CN XII)

• Infrahyoid muscles

Attach hyoid and larynx to sternum and scapula; are antagonists to suprahyoid muscles; depress the hyoid and larynx after having been elevated during swallowing. The infrahyoid and suprahyoid muscles

Figure 30.2

work together to stabilize the hyoid so it can form a solid base for the muscles that move the tongue.

Muscles:
Sternohyoid [ansa cervicalis (motor part of cervical plexus)]
Sternothyroid [ansa cervicalis (motor part of cervical plexus)]. Lies deep to the sternohyoid and attaches to the thyroid cartilage
Thyrohyoid (C1 fibers, by hitching a ride on CN XII)
Runs superiorly from the thyroid cartilage to the hyoid
Omohyoid [ansa cervicalis (motor part of cervical plexus)]
Two bellies (superior and inferior) connected by a tendon

Figure 30.3

Neck ly mph atic dr aina ge , brief intr o

Superficial lymph nodes: lie along the external jugular vein in superficial fascia, and drain scalp, occipital, mastoid,parotid, and superficial face regions. Drain into deep cervical lymph nodes.
Deep cervical lymph nodes: lie deep to SCM, on the carotid sheath along the internal jugular vein.
Deep cervical nodes are grouped in two categories: Superior and inferior deep cervical nodes.
Supraclavicular nodes are the most inferior of the inferior deep cervical nodes. Lymph vessels that drain to these nodes often communicate with the thoracic duct or other large lymph trunks. Thus, lymph from other body regions may filter through supraclavicular nodes. Enlarged supraclavicular nodes are a bad sign – it may reflect metastasis of cancer from distant organs (lungs, stomach).
Deep cervical nodes are the ultimate repository for lymph from all regions of the head and neck. Lymph from the headpercolates through other peripheral sets of nodes first before reaching the deep cervical nodes.

Figure 30.4 Lymph nodesof the neck.

GRAY’ S ANATOMY FORSTUDENTS, 3RD ED., FIG.8.193.

From deep cervical nodes, lymph drains into large jugular lymph trunks. These return lymph to the blood via the thoracic duct or right lymph duct, or by draining directly into the left and right venous angles.

Neck fascia

The neck has several fascial planes which contain many important structures.

Superficial cervical fascia/subcutaneous tissue of the neck. Like all superficial fascia in the body it contains loose connective tissue and cutaneous vessels and nerves. The superficial cervical fascia also contains the following:
Platysma muscles: thin grimace muscles; these are

muscles of facial expression that blend with other facial muscles near the corners of the mouth.

Superficial veins
External jugular vein (EJV): formed just below the angle of the mandible by the union of the retromandibular vein (posterior division) and posterior auricular vein
Crosses outer surface of the SCM in the superficial fascia, just deep to the platysma

Figure 30.5 Platysmamuscle. GILROY, ATLASOF ANATOMY, 2ND ED., THIEME PUBLISHERS, FIG. 3.83D.

Pierces the investing layer of deep fascia at the posterior border of the SCM, then descends to to the midpoint ofthe clavicle to join the subclavian vein
Anterior jugular veins (usually left and right): begin below the chin and pass inferiorly just lateral to the midline.They duck under the SCM and pass laterally to enter the EJVs.
The left and right anterior jugular veins often communicate via a venous arch that passes across the midline of theneck just above the manubrium. If present, it could cause bleeding problems during a tracheotomy procedure.

Figure 30.6 Superficial veins of the neck.

GRAY’ S ANATOMY FOR STUDENTS, 3RD ED., FIG. 8.181.

Figure 30.7

• Deep Cervical Fascia

Supports the viscera, muscles, vessels, and deep lymph nodes
Allows neck structures to move and glide past one another without diﬃculty (e.g. pass bolus down the pharynx, or when turning your head)
Fascial layers may be separated by pus or fluid accumulation, creating a connection where an infection may spread to another body region (e.g. to the mediastinum)
Natural cleavage planes used as guides during dissection and exposing surgical fields
The deep cervical fascia has subparts with specific names. These enclose organs and muscle groups, forming aseries of concentric rings, like those in a tree trunk. However, the layers of deep cervical fascia are connected in certain locations. The most important parts of the deep cervical fascia are: (1) investing layer of deepfascia, (2) pretracheal fascia, (3) prevertebral fascia, and (4) the carotid sheath

Figure 30.8

· Investing fascia

Surrounds the entire neck just deep to the superficial fascia; forms a roof over the neck triangles
Splits to enclose the SCM and trapezius muscles
Attaches to the skull above, spines of cervical vertebrae posteriorly, and the sternum and clavicles below.

· Pretracheal fascia

Limited to the anterior neck (meaning, anterior to the vertebrae)
Attaches to the hyoid bone and laryngeal cartilages superiorly and extends down into the mediastinum to blend with the fibrous pericardium in the thorax inferiorly
2 parts:
Muscular part: thin and surrounds the

infrahyoid muscles

Visceral part: surrounds the thyroid gland, trachea, and esophagus. This layer extends upwards tosurround the pharynx, where it is called buccopharyngeal fascia.

· Prevertebral fascia

Covers the prevertebral muscles anterior to the spine andthe deep extensor muscles in the posterior neck.
Attaches to the base of the cranium and to the spinousprocesses and bodies of the cervical vertebrae
Passes along the spine into the posterior mediastinum inferiorly

· Carotid Sheath

Formed by fusion of the other three layers of deep cervical fascia. Contents: Carotid arteries (common, internal, and external), internal jugular vein, vagus nerve, and nervebranches to the carotid body and sinus
Attached to the outer surface of the carotid sheath are deepcervical lymph nodes.

• Fascial Spaces

Potential spaces exist between the layers of deep fascia in theneck, around the pharynx, and in the floor of the mouth.
Retropharyngeal Space: between prevertebral and visceral pretracheal fasciae, this space is posterior to the pharynx andesophagus and anterior to the cervical vertebral bodies.
Allows movement of the pharynx, esophagus, trachea, andlarynx during swallowing

Figure 30.9

Pretracheal space: between infrahyoidmuscles and trachea; can extend into mediastinum, where the pretracheal fascia blends with the pericardium
Lateral pharyngeal spaces (parapharyngeal spaces): adjacent to the lateral surfaces of the pharynx, between the pharynx and the musclesof the infratemporal fossa. This space communicates posteriorly with the retropharygeal space.

The cer vic al plexus

The cervical plexus supplies motor and sensory branches to the neck,as well as giving rise to the phrenic nerves. The plexus is formed by the intermingling of nerve fibers from the ventral rami of spinalnerves C-1 to C-4. The ventral rami pierce the prevertebral fascia before joining to form the plexus.

Motor branches of the cervical plexus

Phrenic nerves: these are old friends that we encountered previously in the thorax. They are formed by the ventral rami of C-3, C-4, and C-5,although technically only C-3 and C-4 are parts of the cervical plexus. The phrenic nerves descend on the anterior surfaces of the anterior scalene muscles at the root of the neck, then pass through the superior thoracic aperture into the thoracic cavity. You know the rest of the story from here! C-3, C-4, and C-5 – Keep the Diaphragm Alive! The phrenic nerves are motor to the diaphragm and sensory to the pericardium and parietal pleura (mediastinal and diaphragmatic portions).

Ansa cervicalis: This nerve is formed from two roots – a superior root derived from the ventral ramus of C-1 and an inferior root from C-2 and C-3 spinal nerves. The superior root of the ansa “hitches a ride” with the hypoglossal nerve for a distance, before separating from it. The two roots descend along the carotid sheath and unite below to form a loop (ansa is Latin for “loop”). Motor branches from the ansa supply three of the four infrahyoid muscles: sternothyroid, sternohyoid, and omohyoid. Thus, the ansa supplies all infrahyoid muscles, except one = the thyrohyoid. C-1 fibers that also follow the hypoglossal nerve (but are not part of the superior root of ansa), separately innervate the thyrohyoid muscles.

Figure 30.10 Ansa cervicalis nerve. GRAY’ S ANATOMY FOR STUDENTS, 3RD ED., FIG. 8.173.

Sensory branches of the cervical plexus

These emerge along the posterior border of the sternocleidomastoid, pierce the investing fascia, and then enter the superficial cervical fascia. Four branches:

Lesser occipital nerve (C-2): supplies the neck and scalp behind the external ear.
Great auricular nerve (C-2 and C-3): ascends vertically across the SCM, usually posterior to the external jugular vein,to skin over the parotid gland, external ear, and angle of the mandible.
Transverse cervical nerve (C-2 and C-3): crosses the SCM and penetrates the platysma, this nerve is the major sensory nerve of the anterior neck.
Supraclavicular nerves (C-3 and C-4): supply the skin at the base of the neck = over the clavicles and atop the shoulders.

Spasm of the diaphragm muscle produces pain signals that are transmitted in intercostal and phrenic nerves. Since the phrenic nerves originate in the neck, this “stich in your side” pain can also be referred to the C-3 and C-4 dermatomes (recall that these areas are supplied by the supraclavicular nerves). Indeed, runners with diaphragm spasms often complain of pain in their shoulders and neck.

Figure 30.11 Sensory nervesof the neck.

GRAY’ S ANATOMY FORSTUDENTS, 3RD ED., FIG. 8.183.

Figure 30.12 Cutaneous nerves of the neck.

CLINICALLY ORIENTED ANATOMY, 8TH ED., FIG. 9.25 A.

Triangles of the neck

The topography of certain neck muscles produces the borders of triangularspaces. These so-called neck triangles are useful for describing the locations of normal anatomical structures and pathologies in the neck.

Posterior triangle

Boundaries
Posterior: anterior border of trapezius
Anterior: posterior border of SCM
Inferior: middle third of the clavicle
Roof: investing layer of deep cervical fascia
Floor: prevertebral fascia, covering the surfaces of prevertebral muscles.

Contents of the posterior triangle:

Arteries
The transverse cervical and suprascapular arteries(both from the subclavian artery) cross the triangle.
The third part of the subclavian artery is located at the base ofthe triangle, just posterior to the SCM, near the midclavicular point.Distal to this location, the subclavian artery becomes the axillaryartery, supplying the upper limb. Downward pressure with fingerson the subclavian artery in the posterior triangle compresses theartery against the first rib. In an emergency, this is a pressurepoint for the control of bleeding in the upper limb.

Veins
External jugular vein: Enters the subclavian vein at the base of the triangle, just behind the SCM. It was described in the superficial fascia section
Nerves
The Spinal Accessory nerve (Cranial nerve XI) crosses the center of the posterior triangle, after innervating the SCM.
As described earlier, Erb’s point is located halfway down the posterior border of the SCM. The supraclavicularnerves cross the posterior triangle within the superficial fascia.

The proximal parts of the brachial plexus (roots and trunks) pass through the base of the posterior triangle. The roots of the Brachial Plexus (C₅–T₁) exit between anterior and middle scalene muscles and descend between the 1st rib and clavicle,to enter the axilla. The roots will form trunks (upper, middle, and lower).

Figure 30.13 CN XI inposterior triangle.

GRAY’ S ANATOMY FOR STUDENTS, 3RD ED., FIG. 8.170.

Anterior triangle

Boundaries
Medial: anterior midline of neck
Posterior: SCM
Superior: inferior border of the mandible
Recall the hyoid lies in the anterior triangle opposite C3. The anterior triangle above and below the hyoid bone are often called suprahyoid and infrahyoid regions, respectively.

The anterior triangle is subdivided into four smaller triangles.

Figure 30.14

Figure 30.15 Triangles of the neck. GRAY’ S ANATOMY FOR STUDENTS, 3RD ED., FIG. 8.162.

Figure 30.16 Figure 30.17

Submental triangle

This is the least important of the sub-triangles. Borders: hyoid, mandible, and the right and left digastric anterior bellies. The floor is the 2 mylohyoid muscles.
Contents: submental lymph nodes and small veins that unite to form anterior jugular vein

Submandibular triangle

Borders: anterior and posterior bellies of the digastric muscles and the mandible above. The floor is formed by the mylohyoid, hyoglossus, and middle pharyngeal constrictor muscles.

Contents:
Submandibular salivary gland and duct (fills most of the triangle)
Submandibular lymph nodes: receive lymph from the tongue and the oral cavity. Lesions in the mouth (like “canker” sores) can cause their inflammation (lymphadenopathy) and make them tender.
Cranial nerve XII: occipital artery twists around it; passes between mylohyoid and hyoglossus muscles
Nerve to mylohyoid (V₃): innervates the digastric anterior belly and mylohyoid
Lingual artery: to the tongue
Facial artery: spirals around the submandibular gland, then crosses the mandible to reach the face.

Muscular triangle

Borders: neck midline, superior belly of the omohyoid, and anterior border of the SCM.
Contents: infrahyoid muscles and neck viscera The floor muscles are reflected for surgical access to the thyroid gland, larynx, and trachea.

Carotid triangle

Borders: digastric posterior belly, omohyoid superior belly, and anterior border of SCM. Its floor consists of the thyrohyoid, hyoglossus, and all three pharyngeal constrictor muscles.

· Contents: Common carotid artery, carotid bifurcation, carotid sinus and carotid body, ansa cervicalis;, deep cervical lymph nodes, internal jugular vein, vagus nerve (X), and hypoglossal nerve

Figure 30.18

Ov e r v i e w o f c a r ot i d a r t e r i e s i n t h e n e c k

Common Carotid Artery (CCA): ascends and bifurcates at ~C-4 (superior border of the thyroid cartilage) into the internal carotidand external carotid arteries
Carotid sinus (baroreceptor): the enlarged, proximal portion of theinternal carotid artery, just distal to the bifurcation; innervated by CN IX (carotid sinus nerve)
Carotid body (chemoreceptor): a small vascular structure,located outside the vessels, within the carotid bifurcation (“crotch”). Innervated by the carotid sinus nerve (CN IX).
Internal carotid (ICA): NO branches in the neck
External carotid: most branches originate in the carotid orsubmandibular triangles
Three anterior branches
Superior thyroid artery: runs deep to the infrahyoidmuscles and ends at the thyroid gland. It gives rise to the superior laryngeal artery (supplies the larynx).
Lingual artery: passes deep to CN XII and the posteriorbelly of the digastric to enter the tongue deep to the hyoglossus muscle
Facial artery: arises either in common with lingual artery or just superior to it. It passes deep to the digastric anterior belly, loops around and supplies the submandibular gland;then hooks around the

middle of the inferior border of the mandible (feel pulse here) to enter the face. VERY curly Q!

Two posterior branches
Occipital artery: passes posteriorly, immediately medial and parallel to the posterior belly of the digastric twisting around CN XII. Supplies the posterior scalp.
Posterior auricular artery: Passes behind the auricle (external ear), which it supplies, along with the posterior scalp.
One medial branch: The ascending pharyngeal artery arises from the medial side of the artery, just above thecarotid bifurcation. It supplies the pharynx.
2 terminal branches: maxillary and superficial temporal arteries. The superficial temporal artery supplies the scalp. The maxillary artery supplies cavities within the head and is discussed in later chapters.

It’s as easy as 1-2-3 to help you REMEMBER the branches of the external carotid!

medial branch
posterior branches
anterior branches

Then the terminal branches.

Figure 30.19

Figure 30.20 Branches of external carotid artery in the neck.

GRAY’ S ANATOMY FOR STUDENTS, 3RD ED., FIG. 8.167.

Ov e r v i e w o f i n t e r n a l j u g u l a r v e i n

Receives blood from most of the head and neck, including the brain.The scalp and superficial neck are drained by the external jugular.
Begins at the jugular foramen and runs in the carotid sheath with thecarotid arteries and CN X. It leaves the anterior triangle when itpasses deep to the SCM.
Unites with the subclavian vein to form the brachiocephalic vein,posterior to the sternal end of the clavicle.
It is closely associated with the deep cervical lymph nodes.

Ov e r v i e w o f va g u s n e r v e i n t h e n e c k

Pharyngeal branches: motor to pharyngeal constrictor and soft palate muscles
Superior laryngeal nerve: external and internal branches (internalpierces the thyrohyoid membrane with the superior laryngeal artery to enter the larynx). These supply the mucosa of the upper larynx and one muscle of the larynx. Discussed in detail the larynx chapter.
Cervical cardiac branches: nerves to the heart arising in theneck. Why? Because of development, of course!
Recurrent laryngeal nerves: both the left and right nerves pass throughthe neck, but only the right recurrent laryngeal originates from thevagus in the neck
Ascend in the groove between trachea and esophagus to reach larynx
Motor to all muscles of the larynx (except one)
Sensory to mucosa of lower larynx.

31

Root of the neck

OPTIONAL READING

Moore, Clinically Oriented Anatomy, 7th ed., Deep structures of neck section through Nerves in root of neck.

CHAPTER CONTENT S

DEEP NECK AND R OOT OF THE NECK SKELE TAL FR AME W ORK

PRE VERTEBR AL MUSCLES IN THE NECK

DEEP NECK MUSCLES/MUSCLES REL ATED TO THE R OOT OF THE NECK

BLOOD AND LY MPH VESSELS ASSOCI ATED WITH THE R OOT OF THE NECK

NER VES

OT H E R O R G A N S

Root of the neck

The root of the neck (base of the neck, cervicothoracic region) is important because it is the region of continuity between the neck andthorax, and the neck and upper limbs. It can be somewhat confusing since neither the origin nor the destination of many important structures can be seen, yet you must know something about these structures in order to make sense of their functional significance.

Skele tal fr ame w ork

The bony architecture underlying the root of the neck is the superiorthoracic aperture. Structures traverse this opening in order to pass from or to the thorax, neck, and upper limb. Let’s quickly review its boundaries:
T-1 vertebra posteriorly
Suprasternal notch anteriorly
The first ribs laterally

The medial part of the clavicle is also an important landmark in the rootof the neck.

Pre vertebr al muscles in the neck

The scalene muscles, part of the prevertebral group of muscles, figure prominently when describing nerves and vessels in the root of the neck. The three scalene muscles (geometry buﬀs – what is a “scalene” triangle?) are located anterior and lateral to the cervical vertebrae, deep to the sternocleidomastoid. They attach above to the transverse processes of C-3 through C-7 vertebrae and below to the upper two ribs. They function to flex the neck and can also actas accessory respiratory muscles by raising the first two ribs during inspiration. The scalene muscles are covered externally by the prevertebral fascia.
Anterior scalene: inserts onto rib 1; phrenic nerve courses on its surface, subclavian vein passes anterior, and subclavian artery passes posterior
Middle scalene: inserts on the first rib behind the anterior scalene. The gap between the anterior and middle scalene muscles is traversed by the brachial plexus and the subclavian artery
Posterior scalene: small, inserts on rib 2; can be fused with middle scalene. The middle and posterior scalene muscles are located in the floor of the posterior triangle.

Figure 31.1 GRAY’ S ANATOMY FOR STUDENTS, 3RD ED., FIGURE 8.185.

The other muscles in the prevertebral group are the longus capitis andlongus colli (also called longus cervicis). These muscles are in the deep neck, posterior to the neck viscera (pharynx, esophagus). Like the scalene muscles, they are covered by prevertebral fascia. The longus capitis attaches above to the occipital bone and below to the cervical vertebrae. The longus colli attaches above and below to the bodies and transverse processes of cervical vertebrae. These muscles flex the head and neck. The details of these muscles are not too important, but they are landmarks for locating the sympathetic trunks, which we will see in lab.

Blood and ly mph vessels associ ated with the r oot of the neck

Subclavian arteries: these have diﬀerent origins (review these!), but similar

courses in the root of the neck. Both subclavian arteries arch over the lung apices posterior to the anterior scalene muscles and dive deep tothe middle part of the clavicle. Their branches are best studied by dividing the artery into three parts, based on its relationship to the anterior scalene muscle:

Part I: medial to anterior scalene; the lung apices, cervicalpleura, and sympathetic trunks lie posteriorly
Part II: deep to anterior scalene
Part III: lateral to anterior scalene
Beyond the first rib, the subclavian artery changes its name to become the

axillary artery.

Three large branches arise from Part 1, one small branch arisesfrom Part 2, and typically there are no branches from Part 3.However, variations do occur.
Vertebral artery: From Part 1 – ascends through the transverse foramina

of cervical vertebrae 1 through 6 (misses the 7th) and enters the skull through foramen magnum. The two vertebral arteries fuseto form the basilar artery in the cranial cavity

Thyrocervical trunk: short stump from Part 1, near the medialborder of anterior scalene – gives oﬀ three major branches
Suprascapular artery: crosses anterior scalene, phrenic nerve, and brachial plexus; dives deep to clavicle; suppliesscapula and scapular muscles
Transverse cervical artery: Crosses the anterior scalenemuscle and brachial plexus, parallel to and above thesuprascapular artery, then crosses the posterior triangle of the neck. It usually divides into a superficial and deep branch. These supply the brachial plexus, trapezius muscle, and scapular muscles in the back.
Common variation: the deep branch of the transverse cervical artery may be absent – instead, it may arisedirectly from the 3rd part of subclavian artery. If this is the case, this variant artery is called the dorsal scapular artery

Inferior thyroid artery: the largest branch of the thyrocervical trunk. Passes medially, behind the carotid sheath and anterior to the longus colli muscle. Serves the thyroid and parathyroid glands as well as the larynx.
Internal thoracic artery: remember this guy from our study of the chest wall? Sure you do! It arises from Part 1 of the subclavian artery and heads south, deep to the costal cartilages and parallel to the lateral borders of thesternum. Supplies the chest wall, diaphragm, and anterior abdominal wall (via its superior epigastric branch).
Costocervical trunk: From Part 2. Variable and small – normally gives oﬀ two branches that supply the deep neckand upper intercostal spaces. Not too important.
Subclavian vein: the continuation of the axillary vein, proximal to rib 1; it courses superficial to the anterior scalene muscle and below the clavicle.
Deep to sternoclavicular joint: joins internal jugular vein to form the brachiocephalic vein
Only constant tributary: external jugular vein

Figure 31.2 Branches of the subclavian arteries. Note relationship to anterior scalene muscle.

GRAY’ S ANATOMY FOR STUDENTS, 3RD. ED., FIG. 8.187.

Thoracic duct: passes from the mediastinum into the neck via the superior thoracic aperture, posterior to the esophagus
Arches to the left, deep to the carotid sheath and anterior to the arterial branches of the subclavian artery, theanterior scalene muscle, and the phrenic nerve
Usually empties into the junction of the left subclavian and internal jugular veins (the left venous angle)
Normally receives lymph from all regions of the body below the diaphragm, left side of the thorax, left side of the head and neck, and left upper limb (~ 75% of the body’s lymph drainage).
Right lymph duct: formed by the union of lymph trunks from the right side of the thorax, right side of the head and neck, and right upper limb (~ 25% of body’s lymph). Enters the junction of the right subclavian and internal jugular veins (right venous angle). Frequently, the trunks do not unite to form the right lymph duct, but drain independently to the venous system.

Figure 31.3 GRAY’ S ANATOMY FOR STUDENTS, 3RD ED., FIGURE 8.191.

Figure 31.4 Variation inlymph ducts and trunks atroot of neck.

GRAY’ S ANATOMY FORSTUDENTS, 3RD ED., FIG.8.192.

CLINIC AL APPLIC ATION

Central Venous Access is a procedure used to place a catheterin a large vein. The venous access site depends on the reason for the placement and the anatomy of the patient. Large veins at the root of the neck (subclavian and internal jugular veins) are often selected. A subclavian approach places the catheter in the subclavian vein under the middle third of the clavicle. An internal jugular insertion is done between the sternal and clavicular heads of the sternocleidomastoid, lateral to the pulsations of the common carotid artery. Usually the right internal jugular vein is selected because it is more vertically in-line with the SVC and there are less complications on the right side, given that the left dome of the lung rises higher into the neck and the thoracic duct is on the left.

Ner ves

Brachial plexus: somatic nerve plexus, originates in root of the neck, and terminates in the axilla, where it gives oﬀ large nerves that supply the upper limb. Smaller branches are given oﬀ in the neck, supplying muscles of the pectoral girdle, primarily those that move the scapula.
We will tackle the brachial plexus in detail when we study the upper limb. For now, realize that the roots of the plexus(ventral rami of spinal nerves C-5, C-6, C-7, C-8, and T-1) emerge from the vertebral column between the anterior and middle scalene muscles in the root of the neck.

CLINIC AL APPLIC ATION

THOR A CIC OUTLE T SY NDR OME

Compression or irritation of the brachial plexus and/or subclavian artery in the region between the clavicleand first rib, through which nerves and vessels reach the upper limb

Can produce variety of symptoms: pain, numbness, tingling, weakness, or coldness in upper limb
Caused by any number of anatomic circumstances:
Compression of the inter-scalene space (between anterior and middle scalene muscles)
Costoclavicular approximation: reduced space between clavicle and rib 1 (due to trauma or postural problems)
An extra rib (cervical rib) or extra-long transverse process of C7
Compression by the tendon of pectoralis minor muscle

• Vagus nerves and Recurrent Laryngeal nerves

Right: crosses anterior to right subclavian artery; gives oﬀ right recurrent laryngeal nerve that loops posterior to the right subclavian artery in the root of the neck.
Left: enters the superior mediastinum between the left common carotid and left subclavian arteries; recall that the left recurrent laryngeal nerve originates in the mediastinum, not in the root of the neck
Both recurrent laryngeal nerves: ascend in

tracheoesophageal grooves to reach larynx

Sympathetic trunk: lies posterior to the carotid sheath, deep to the prevertebral fascia, and anterior to the longus capitismuscle. Ascends into the deep neck via the superior thoracic aperture.
Does not have chain ganglia associated with each spinal nerve; instead, the original eight embryonic ganglia fused into3 or 4 cervical chain ganglia. Much variation in arrangement! There seem to be two consistent, large sympathetic ganglia in the neck.

Figure 31.6 Vagus and phrenic nerves at the root of the neck. Note the relationship of the subclavian vessels and anterior scalene muscle. GRAY’ S ANATOMY FOR STUDENTS, 3RD ED., FIG.

8.188.

Cervicothoracic ganglion (stellate ganglion): lies anterior to the neck of rib 1, posterior to the vertebral artery origin; formed by the fusion of the first thoracic ganglion and the lowest cervical ganglion.
Superior cervical ganglion: the largest and highest ganglion of the

sympathetic trunk – lying opposite C2. Contains ALL of the postganglionic sympathetic neuron cell bodies that innervate tissues in the head.

Take heart, there are some constants regarding cervical chain ganglia:
They all have gray rami communicantes connected to cervical spinal nerves (several spinal nerves may receivegray rami from one ganglion). What is their function?
They all give oﬀ tiny cervical cardiac nerves, which pass through the superior thoracic aperture to the cardiac autonomic nerve plexus. Function?

Figure 31.7 NET TER, ATLAS OF HUMAN ANATOMY, 8TH ED., PLATE 142 (REVISED).

Ot h e r o r g a n s

Trachea and esophagus: pass through the center of the superior thoracic aperture. The trachea can be easily palpatedjust above the suprasternal notch. In the tracheoesophageal groove between are the recurrent laryngeal nerves.
Apices of the lungs (covered by cervical pleura): project above the level of the

first rib, through the superior thoracic aperture into the root of the neck

The subclavian artery and vein groove the pleura just anterior to the apex.
Note that the lungs and pleura are vulnerable to injuries in the region of the supraclavicular fossa. Trauma to the root of the neck can produce a pneumothorax!

Figure 31.8 Cervical pleura rises into the root of the neck through the superior thoracic aperture. GRAY’ S ANATOMY FOR

STUDENTS, 3RD ED., FIGURE 8.186.

ADDITIONAL DETAILED VIDEOS FOR YOUR STUDY

4.1.12 Anterior neck muscles.

4.9.1 Subclavian and common carotid arteries.

4.9.8 Branches of thyro-cervical trunk; externalcarotid artery and its branches (just thyrocervical trunk).

1.1.14 Nerves of the shoulder region: the brachial plexus (intro through divisions and trunks)(BP intro, and suprascapular nerve and after).

4.8.14 Sympathetic trunk, cervical plexus(sympathetic trunk part).

32

Overview of neck viscera; thyroid and parathyroid glands

OPTIONAL READING

Moore, Clinically Oriented Anatomy, 7th ed., Viscera of neck section through Nerves of parathyroid glands.

CHAPTER CONTENT S

OV E R V I E W O F N E C K V I S C E R A ; T H Y R O I D A N D PA R AT H Y R O I D GL ANDS

RESPIR ATOR Y L AY ER = L AR Y NX AND TR A CHEA DIGESTIVE L AY ER = PHARY NX AND ESOPHA GUS

ENDOCRINE L AY ER = TH Y R OID AND PAR ATH Y R OID GL ANDS LY M P H AT I C D R A I N AG E O F T H E H E A D A N D N E C K

Overview of neck viscera; thyroid and parathyroid glands

In thinking about the overall architecture of the neck, it can be organized into 4 units:

The visceral unit contains the neck’s visceral organs (the focus of this chapter). It is located anteriorly.
The vertebral unit is posterior; it contains the vertebral column and its associated muscles, and the spinal cord.
Two vascular units are located anterolaterally. These are essentially the carotid sheaths and their contents.

The viscera of the neck themselves can be further organized into three diﬀerent layers: respiratory, digestive, and endocrine. Each of these layers contains two organs. An overview of the neck

Figure 32.1 The visceral unit of the neck.

CLINICALLY ORIENTED ANATOMY, 8TH ED., FIGURE 9.28.

viscera is provided in this chapter as well as a detailed description of the thyroid and parathyroid glands. All the neck viscera are covered by thepretracheal layer of deep cervical fascia and lie in the floor of the muscular triangle, deep to the infrahyoid muscles.

Respir ator y l ay er = l ar y nx and tr a chea

Larynx: lies between C4–6; its thyroid and cricoid cartilages canbe palpated easily
Continuous inferiorly with the trachea.
Laryngeal prominence (“Adam’s apple”) of the thyroid cartilage:projects as a midline ridge.
Below the thyroid cartilage, the rounded cricoid cartilage of the larynx is

palpable.

The larynx is covered in more detail in chapter 33.
Trachea: begins at C6 just below the cricoid cartilage and passesinferiorly into the mediastinum. Its superficial location allows it to be easily palpated just above the bony suprasternal notch. The textureof the trachea is characterized by the presence of cartilage rings.
The upper part of the trachea is covered anteriorly by theisthmus of the thyroid gland.

Digestive l ay er = phar y nx and esopha gus

The pharynx (“throat”) is a muscular tube common to the respiratory and digestive tracts. It is located posterior to the nasal and oralcavities and anterior to the skull base and cervical vertebrae. It serves as both an airway and a route for ingested solid foods and liquids. Thepharynx is covered in detail in chapter 36.
Cervical esophagus: lies immediately posterior to the trachea,commencing below the pharynx at the level of C-6 (the same level where trachea begins)
The Recurrent laryngeal nerves pass superiorly in the tracheo-esohageal grooves.
Paratracheal lymph nodes also lie between the trachea and esophagus.

Endocrine l ay er = th y r oid and par ath y roid gl ands

Thyroid and parathyroid glands: lie deep to infrahyoid (strap) muscles, in the

floor of the muscular triangle. A fibrous capsule derived frompretracheal fascia surrounds them.

Thyroid gland: constructed of a median isthmus and two laterallobes. Each lateral lobe has a superior and an inferior pole.
Isthmus: connects the two lateral lobes; lies anterior to 2nd–4thtracheal cartilage rings

Sometimes a pyramidal lobe of the thyroid projects superiorlyfrom the isthmus in the midline of the neck. This is a commonvariation in which thyroid tissue develops along the course ofthe thyroglossal duct, which is a vestige of thyroid development (covered in chapter 34).
Blood supply: rich blood supply, as would be expected for an endocrine

organ. The superior thyroid arteries are the first branches of the external carotid arteries); the inferior thyroid arteries are branches from the thyrocervical trunk via the subclavian arteries. Thesevessels anastomose freely within the gland.

Thyroid ima artery: variant (~ 8%); branch of thebrachiocephalic trunk, passes upward to the isthmus, superficial to the trachea.
Venous drainage: superior and middle thyroid veins drain to internal jugular vein; the inferior thyroid veins drain below intothe brachiocephalic veins, and overlie the trachea.
Lymphatic drainage: paratracheal and deep cervical nodes
Basic functions: thyroid hormones are produced by the follicular cells of the thyroid gland. They function to controlmetabolism rate; Calcitonin is a hormone produced by the parafollicular (“C”) cells of the thyroid – it functions to lowerblood levels of calcium. Follicular and parafollicular cells have diﬀerent development histories, as well shall see.

The development of the thyroid gland is covered in chapter 34.

· Pathologies and Congenital Defects

Goiter (enlargement of the gland) can be caused by several factors
Thyroglossal duct cysts: located in the midline of the neck and represent a persistent thyroglossal duct between the tongue and the neck, which forms a cyst.
Thyroid tumors: benign and malignant, are fairly common

Figure 32.2 Thyroid gland. NET TER, ATLAS OF HUMAN ANATOMY, 7TH ED., PLATE 87.

Ectopic thyroid tissue: may be found on the back of thetongue (lingual thyroid), and/or below the chin in the midline of the neck. Because the thyroid forms in the back of the tongue and later moves into the neck, ectopic tissue is not uncommon. More discussion of this in chapter 34.
Parathyroid glands: reddish-brown, usually four in number (left and right,

superior and inferior), and lie in the capsule on the posterior surface ofthe thyroid gland

Blood supply and venous/lymphatic drainage follows thepattern of the thyroid gland.
Function: they produce parathyroid hormone (parathormone), which functions to elevate the levels of blood calcium (bystimulating osteoclast activity in bone), helps to regulate serumphosphate levels, and promotes vitamin D synthesis.
The development of the parathyroid glands is covered in chapter 34.

Figure 32.3 Relationships of thyroid and parathyroid glands, inferior thyroidartery, and recurrent laryngeal nerve. NET TER, ATLAS OF HUMAN ANATOMY,7TH ED., PLATE 89.

Ly m p h at i c d r a i n a g e o f t h e h e a d a n d n e c k

Terminal lymph drainage from the head and neck is via deep cervicalnodes that lie on the carotid sheaths, closely associated to the internal jugular veins. Lymph from the deep cervical nodes enters the left andright jugular lymph trunks. These may join the subclavian or internal jugular veins independently, or they may join the right lymph duct on the right side, and the thoracic duct on the left side, which drain to the left and right venous angles (jugulosubclavian junctions).

The deep cervical nodes receive lymph from peripheral (outlying)nodes in the head and neck. The peripheral nodes in the neck can beroughly organized into superficial and deep groups.

Superficial group of peripheral nodes: collect lymph from thesuperficial fascia and skin of the neck
Anterior jugular nodes and external jugular nodes, located along theveins of the same name. Lymph from these nodes enters deep cervical nodes.
Deep group of peripheral nodes: collects lymph from tissuesDEEP to the investing layer of deep fascia.

These are the paratracheal, pretracheal, and retropharyngeal lymph node.

The deep cervical nodes themselves are divided into a superior group andan inferior group:

Superior Deep Cervical Nodes: lie along the internal jugular veins,superior to the omohyoid muscles. One of the largest of the superior deep cervical nodes receives a special name:
Jugulodigastric node: located where the posterior belly ofdigastric crosses the internal jugular vein; large node that receivesdrainage from the palatine tonsil, and is often enlarged in tonsillitis(the “tonsillar node”); also receives lymphatic drainage from the posterior one-third of the tongue
Inferior Deep Cervical Nodes: located along the internal jugular vein at the

level of and below where it is crossed by the omohyoid muscle

Jugulo-omohyoid node: large and important deep cervical node receives most of the lymph drainage from the anterior part of the tongue and oral cavity (from submental and submandibularlymph nodes draining the lips, chin, and tongue)
Supraclavicular nodes: the most inferior group of inferiordeep cervical nodes

These are clinically important nodes because they are connected to the large lymph ducts at the root of the neck via small communicating lymphatic channels. Lymph in these ducts (thoracic duct on the left, right lymph duct on the right), which originates from large areas of the body, could percolate backwards through lymph channels into supraclavicular nodes, and it is therefore possible that cancer cells from distant organs could wind up in nodes at the base of the neck.

Nice to know – but not need to know: Surgeons have devised schemes for organizing the head and neck lymph nodesinto regions or “levels”. Infectious agents and tumor cells from certain regions of the head and neck (and even distant regions of the body) predictably migrate to nodes in particular levels.

Figure 32.4 Lymph from the entire body drains to the left and right jugulosubclavian junctions (aka = left and rightvenous angles) – indicated by the red circles. Stomach carcinoma may metastasize to the left supraclavicular lymph nodes. Systemic lymphomas may also spread to deep cervical lymph nodes by this pathway.

Figure 32.5

33

Larynx

OPTIONAL READING

Moore, Clinically Oriented Anatomy, 7th ed., Larynx section through Nerves of larynx.

CHAPTER CONTENT S LA R Y N X

FUNC TIONS OF THE L AR Y NX CA R T I L A G E S O F T H E LA R Y N X

LA R Y N G E A L C AV I T Y ( A I R WAY O F T H E LA R Y N X ) FIBR O -EL ASTICMEMBR ANES

LA R Y N G E A L M U S C L E S

INNER VATION OF THE L AR Y NX ( CN X)

BLOOD SUPP LY AND LY MPH ATIC DR AINA GE OF THE L AR Y NX EMBR YOLOGY OF THE LAR Y NX

TR A CHEA

Larynx

The larynx is an organ of the respiratory system and the part of the airway situated between the pharynx and trachea. It is located anterior to the lower pharynx and esophagus, between the levels of C-4 to C-6 vertebrae. Textbooks consider thelarynx to be the most inferior part of the upper respiratory tract. It consists of cartilages, ligaments, skeletal muscles, vocal folds, a mucosal lining, nerves, and arteries. The “skeleton” of the larynx is composed of cartilage. The larynx is a superficial structure – several of its cartilages are easily visible and palpable on the surface of the neck. Therefore, it is vulnerable to injury due to penetrating wounds or blunt trauma.

Func tions of the l ar y nx

Phonation (sound production) (≠ speech production)
Regulates the amount of air entering the trachea and lungs
Acts as a valve to prevent ingested food or liquids from entering the airway – this may be the most important function of the larynx.

When it is removed (laryngectomy) because of laryngeal cancer, the trachea can be connected to an opening in the anterior neck (tracheostomy).

Figure 33.1

Ca r t i l a g e s o f t h e l a r y n x

Thyroid cartilage (L=shield): superior border is located at C4
Largest but incomplete cartilage; it is entirely open posteriorly.A visual analogy is an open textbook, standing upright.
Two flat surfaces laterally = Laminae; they are fused in the midline to form the laryngeal prominence (“Adam’s apple”). Theprominence is the spine of the textbook in our analogy. Males have larger thyroid cartilages than females and the angle between thelaminae is more acute, causing the Adam’s apple to be more prominent.
To the laminae are attached the inferior constrictor,sternothyroid, and thyrohyoid muscles
Superior horn of thyroid cartilage: connected superiorly to thehyoid via the thyrohyoid membrane
Inferior horn of thyroid cartilage: articulates with the cricoidcartilage at the cricothyroid joints, which help to adjust thelength of the vocal folds
Cricoid cartilage (Gr. Krikoeides “ring-shaped”)
Shaped like a “signet (class) ring”. The only laryngeal cartilage that completely surrounds the airway. Has a shortarch anteriorly and a tall lamina posteriorly.
Attached to the first tracheal ring by a ligament

Cricothyroid ligament (cricothyroid membrane): can be easily palpated subcutaneously in the neck as a soft spot betweenthe arch of the cricoid cartilage below and the thyroid cartilage above.

• Epiglottis

Elastic cartilage covered by a mucous membrane; functions to cover the laryngeal opening (inlet) when swallowing
Attached by ligaments to both the thyroid cartilage and hyoid bone
Laryngeal inlet: entrance to the larynx anterior to the pharynx; anterior border of the inlet is formed by the free margin of the epiglottis
Aryepiglottic folds: lateral mucosal borders of the inlet extending from arytenoid cartilages (described next) to the epiglottis
The epiglottis is attached to the root of the tongue by three mucosal folds = these are the glosso-epiglottic folds.
The epiglottic valleculae are the two depressions between the glosso-epiglottic folds. These are importantlandmarks for tracheal intubation procedures.
Arytenoid cartilages (2) – these are pyramid-shaped cartilages that are perched atop the lamina (posterior part) of the cricoid cartilage. They are covered by a mucous membrane. The bases of arytenoid cartilages have two processes = vocal and muscular.

Figure 33.2

Vocal process: project anteriorly – the vocal folds (“vocal cords”)attached here. Muscular process: project laterally – attachment of posterior and lateral cricoarytenoid muscles
Crico-arytenoid joints: articulation with the cricoid lamina; thearytenoid cartilages move atop the cricoid cartilage = they can rotate and glide.
Movement of the arytenoid cartilages abduct or adduct the vocalfolds, thus widening or narrowing the space between the vocal folds.

La r y n g e a l c av i t y ( a i r way o f t h e la r y n x )

The cavity (airway) of the larynx is lined by a mucous membrane. Itsparts are named as are the mucosal folds in its lateral walls.
Two mucosal folds project into the laryngeal cavity and define thespaces of the interior larynx (more on these folds below in the “Fibroelastic Membranes” section)
Vestibular folds – “false” vocal folds – because they do not function to produce sound. The space between the vestibular foldsin the midline of the airway is the rima vestibuli.
Vocal folds (“vocal cords”) – these are the “true” vocal folds,since they produce sound when vibrated. The space betweenthe vocal folds in the midline of the airway is the rima glottidis.

Internal spaces from superior to inferior:
Inlet (Aditus): connects the airway of the larynx to the pharynx.Located between the aryepiglottic folds and epiglottis. The inlet faces posteriorly.
Vestibule: the part of the laryngeal cavity between the inletabove and the vestibular folds below.
Ventricle: lateral recesses between the vestibular and vocal folds
End superiorly in blind pouches behind the vestibular folds called

saccules

Infraglottic cavity: the part of the laryngeal cavity below thevocal folds, between them and the first cartilage ring of the trachea
Glottis: the glottis is defined as the part of the larynx that produces sound. The structures that make up the glottis therefore are the vocal folds + rima glottidis (the space between vocal folds).The vestibular folds do not produce sound, so they are not part of the glottis.
Clinicians use the glottis as a landmark for describing diseases andlesions = supraglottic or infraglottic.
FYI – Singers know about the glottis, because certain vocal techniquesmake use of an open glottis or sudden closures of the glottis (“glottal stops”).

Fibr o -el astic membr anes

The lateral walls of the laryngeal cavity are supported by fibro-elasticmembranes deep to the mucosa. These impart rigidity to the mucosal folds as well as elastic flexibility.

• Quadrangular membrane

Submucosal sheet of fibro-elastic tissue, extending between the ary-epiglottic folds above to the vestibular folds below.
Vestibular ligaments: free inferior margins of the quadrangular membranes. These stretch from the internal aspect of the thyroid cartilage anteriorly to the arytenoidcartilages posteriorly. The mucous membrane covered vestibular ligament is the vestibular fold – the ligament is the fibro-elastic core of the fold that gives it stability.
The vestibular folds are not used to phonate – instead, theirfunction appears to be to protect the airway and to assist thevocal folds in closing the airway when performing a Valsalvamaneuver (the “bearing down” technique used when lifting aheavy object or when increasing

intra-abdominal pressure to defecate).

Rima vestibuli: space between the vestibular folds

• Conus elasticus

Submucosal sheet of fibro-elastic tissue, extending between the internal surface of the cricoid cartilage below to the vocal folds above. Vocal ligaments: thickened free upper margins of the conus elasticus. These stretch from the internal aspect of the thyroid cartilage anteriorly to the vocal processes of the arytenoid cartilages posteriorly. Themucous membrane covered vocal ligament is the vocal fold (vocal cord) – the ligament is the fibro-elastic core of the vocal fold.
Rima glottidis: opening between the two true vocal folds

Figure 33.3 Coronal section of laryngeal cavity. The fibro-elastic membranes deep to the mucosa are diagrammed: Quadrangular membrane deep to the vestibular folds and the conus elasticus deep to the vocal folds. HAND DRAWN CONLEY-GRAM.

Table 33.1 Intrinsic muscles of the larynx

Muscle	Action	Innervation
Muscles that aﬀect the position of the vocal folds and size of the rima glottidis
Posterior crico-arytenoid	Rotate arytenoid cartilages to abduct the vold folds Widen rima glottidis	Recurrent laryngeal nerve
Lateral crico-arytenoid	Rotate arytenoid cartilages to adduct volds folds Narrow rima glottidis	Recurrent laryngeal nerve
Transverse arytenoid	Slides arytenoid cartilages medially to adduct vocal folds Close the posterior part of the rima glottidis. Work with thelateral crico-arytenoid to completely seal the airway	Recurrent laryngeal nerve
Muscles that aﬀect the tension on the vocal folds
Cricothyroid	Tilt thyroid cartilage forward to tense the vocalfolds Raise the pitch of the voice	External laryngeal nerve
Thyro-arytenoid	Approximate the arytenoid cartilages to the thyroid cartilageto relax the vocal folds Lower the pitch of the voice	Recurrent laryngeal nerve
Vocalis	Medial-most fibers of the thyro-arytenoid; located within thevocal folds. Muscle fibers insert directly on the vocal ligament. Tenses and thickens segments of the vocal fold to vary thetonal qualities and pitches of the voice.	Recurrent laryngeal nerve

La r y n g e a l m u s c l e s

The skeletal muscles that act upon the larynx can be organized into twocategories:

Extrinsic laryngeal muscles: move the larynx as a whole:infrahyoid muscles depress it; suprahyoid muscles and stylopharyngeus muscle elevate it
Intrinsic laryngeal muscles: alter length or tension of the vocal ligaments,or

change the size and shape of the rima glottidis. A table thatsummarizes the intrinsic muscles of the larynx is provided below.

Innervation: recurrent laryngeal (all intrinsic muscles, except one) and

external laryngeal nerves (one intrinsic muscle = the cricothyroid)

Figure 33.4

Figure 33.5

Figure 33.6

Figure 33.7

Figure 33.8

Figure 33.9

In addition to their eﬀects on vocal quality, intrinsic muscles also act as sphincters, bringing the ary-epiglottic, vestibular, and vocal folds together Workingtogether, intrinsic muscles of the larynx can completely close the airway when we swallow, hold our breath, or perform a Valsalva maneuver.

Inner vation of the l ar y nx ( cn x)

Superior laryngeal: branches oﬀ the vagusnerve just below the jugular foramen.
External branch (motor): Also called the external laryngeal nerve. Descends posterior to the sternothyroid with thesuperior thyroid artery. It lies on the inferior constrictor muscle.
Supplies: inferior constrictormuscle and cricothyroid muscle.
Internal branch (sensory): Also called theinternal laryngeal nerve. Pierces the thyrohyoid membrane (with superior laryngeal artery)
Sensation to the mucosa of the laryngeal cavity

above the vocal fold and including the vocal fold.

• Recurrent laryngeal

Runs in the tracheo-esophageal groove
Enters the larynx by passing deep to theinferior border of the inferior constrictor muscle with the inferior laryngeal artery.
Supplies all the intrinsic muscles of the larynx,EXCEPT the cricothyoid.
Sensory to the mucosa of the laryngeal cavitybelow the vocal fold inferiorly into the trachea

Blood supp ly and

LY M P H AT I C D R A I N A G E O F THE L AR Y NX

Arterial supply
Inferior laryngeal artery: from the inferior thyroid artery
Superior laryngeal artery: from the superior thyroid artery
Venous drainage
Inferior and superior laryngeal veins, then into superior, middle, or inferior thyroid veins
Lymphatic drainage
Lymphatics drain along the blood vessels upwards and downwards, to superior and inferior deep cervical nodes.

Figure 33.10

Embr yology of the l ar y nx

Briefly: how the pharyngeal arches contribute to the development of thelarynx and its innervation

Laryngotracheal groove appears in floor of caudal end of anterior foregut
Evaginates into a respiratory diverticulum which separates frompharynx; a septum grows and separates the diverticulum from the esophagus
Opening of laryngotracheal tube becomes primordial laryngeal inlet
Endoderm gives rise to the internal lining of the larynx.
The cartilages and muscles are derived from mesenchyme in thefourth and sixth pharyngeal arches (discussed in chapter 34) that migrates around the proximal part of the respiratory diverticulum.
Because the larynx originates from the 4th and 6th pharyngeal arches, it is supplied by the vagus nerves (CN X). The superior laryngealnerve innervates derivatives of the 4th arch while the recurrently laryngeal nerves supply derivatives of the 6th arch.

Tr a chea

1 inch in diameter in adults
Extends from the inferior end of the larynx into the thorax
“C” shaped hyaline cartilage rings, with the posterior open endsconnected by smooth muscle (trachealis)
Common carotid arteries and lobes of the thyroid gland are locatedlateral to the trachea

34

Head and neck development

OPTIONAL READING

Moore, The Developing Human, chapter 9, Pharyngeal arches section through figure

9-22; Development of salivary glands section through Development of face.

CHAPTER CONTENT S

HEAD AND NECK DE VELOP MENT THE PHAR Y NGEALAPPAR ATUS

CO M P O S I T I O N O F A P H A R Y N G E A L A R C H

Details of the individual pharyngeal arches

First arch Second arch Third arch

Fourth and sixth arches

How does the smooth contour of the neck result?

PHAR Y NGEAL POUCHES PHAR Y NGEAL CLEFT S

PHAR Y NGEAL MEMBR ANES

DE VELOP MENT OF THE FA CE AND PAR OTID GL AND DE VELOP MENT OFTHE TH Y R OID GL AND

CHAPTER SUMM AR Y

Head and neck development

Most of the events that produce the definitive anatomy of the head and neck are covered in thischapter. The sources of the primordial tissues (pharyngeal apparatus) are first discussed,followed by detailed discussions of the development of the face and thyroid gland. The development of other head and neck organs are discussed with their gross anatomy in later chapters.

The phar y ngeal ap par atus

Beginning in Week 4, the basic tissues of development in the cranial region of the embryo become organized into the pharyngeal apparatus, formerly

Figure 34.1 LANGMAN’ S MEDICAL EMBRYOLOGY, FIGURE 17.6.

called the branchial apparatus, since it resembles gill slits in fish. It isthe forerunner of head and neck structures.

The pharyngeal apparatus is constructed of four components:
Pharyngeal arches
Pharyngeal pouches
Pharyngeal clefts (grooves)
Pharyngeal membranes
Most congenital anomalies in the head and neck region resultfrom faulty transformation of the pharyngeal apparatus intoadult structures.

Co m p o s i t i o n o f a p h a r y n g e a l a r c h

The pharyngeal arches support the lateral walls of the pharynx (theupper part of the foregut).
Human embryos have five pairs of discernable arches, numbered one, two, three, four, and six. The fifth arch in humans either does not develop or is rudimentary and quickly regresses. The sixth archescannot be seen externally.
Similar to other tissues in the embryo, the pharyngeal arches develop in a cranial to caudal sequence, with the upper arches appearingearlier. The arches are separated externally by pharyngeal clefts and internally by pharyngeal pouches.

Each arch is composed of these tissues:

Mesenchyme derived from paraxial mesoderm = gives rise to skeletal muscles.
Neural crest which migrates from the region of the developing brain = gives rise to skeletal structures and connective tissues.
A cartilage bar made from neural crest – this is a temporary structure thought to give initial support to the pharyngeal arch – later it is transformed into other structures (often bone, adult cartilage, or ligament).
External layer of ectoderm.
Internal layer of endoderm.
A cranial nerve (or cranial nerve branch).
An artery (derived from the aortic arches – these were introduced with heart development).

Figure 34.2 Composition of pharyngeal arch, with cranial nerves and aortic arch arteries. LANGMAN’ S MEDICAL EMBRYOLOGY,

FIGURES 17.4, 17.6, AND

17.7.

Details of the individual pharyngeal arches

First arch

Subdivides into a cranial maxillary process and a caudal mandibular process.

These produce the upper and lower jaws, respectively.

Neural crest condenses to form the transient cartilage of themaxillary process and cartilage of the mandibular process (Meckel’s cartilage). From these cartilages develop the incus and malleus – bones of the middle ear.
Mesenchyme from neural crest forms the substrate for facial bones thatdevelop via intramembranous ossification = maxillae, mandible,zygomatic bones, and the squamous part of the temporal bones.Maldevelopment of the first arch can produce facial abnormalities.
Mesenchyme from paraxial mesoderm gives rise to muscles associated with the first arch = mastication muscles (temporalis, masseter, medial and lateral pterygoid) as well as the mylohyoid, anteriorbelly of the digastric muscle, the tensor tympani (middle ear) and tensor veli palatini (soft palate).
The cranial nerve associated with the first arch is the trigeminal(cranial nerve V) – but only its maxillary and mandibular divisions (V₂ and V₃).
The first aortic arch artery regresses as the first pharyngeal arch develops. It probably only contributes to a small portion of thedefinitive maxillary artery.

Second arch

Neural crest cells form the cartilage of the second arch (Reichert’s cartilage). From the cartilage develops the stapes(middle ear), the styloid process of the temporal bone, the stylohyoid ligament, and the lesser horns and upper part of the body of the hyoid bone.
Mesenchyme from paraxial mesoderm of the second pharyngeal arch migrates across the developing face to form mimetic muscles (muscles of facial expression), as well as the posterior belly of the digastric and stylohyoid muscles in the neck, and the stapedius muscle (in the middle ear).
The cranial nerve of the second arch is the facial nerve (cranial nerve VII).
The second aortic arch artery regresses as the second pharyngeal arch develops. Its only vestige is the small stapedial artery of the middle ear.

Third arch

Neural crest of the third arch produces the cartilage of the third arch. From this cartilage develops the greater horn and thelower part of the body of the hyoid bone. Thus, the hyoid bone is a composite structure built from two pharyngeal arches.
Mesenchyme from paraxial mesoderm of the third arch produces only the

stylopharyngeus muscle of the pharynx.

The cranial nerve associated with the third arch is the glossopharyngeal nerve

(cranial nerve IX).

Figure 34.3

As described when we studied the development of the heart, the third aortic arch arteries give rise to the major arteries of the head: left andright common carotid arteries and the proximal portions of the internal carotid arteries.

Fourth and sixth arches

These arches are usually considered together since they combine togive rise to the larynx. Some sources claim that a true separate sixth arch does not exist.
The cartilages of the larynx are formed from the embryonic cartilages of the fourth and sixth pharyngeal arches. There is debate among embryologists concerning the source of mesenchyme for thesecartilages. Some authors claim neural crest, while others suggest lateral mesoderm from the trilaminar disc is the source. Most authors do agree that the epiglottic cartilage develops much later than the other laryngeal cartilages, perhaps as late as the 5th month.
Mesenchyme from paraxial mesoderm of the 4th and 6th arches givesrise to its muscles: pharyngeal constrictor muscles (superior, middle, and inferior), intrinsic muscles of the larynx (muscles of phonation = produce sound), the levator veli palatini (soft palate), and the palatoglossus muscles (associated with tongue and soft palate).
The vagus nerves (cranial nerve X) innervate the fourth and sixtharches. More precisely, the superior laryngeal nerves supply the fourth arches, while the recurrent laryngeal nerves supply the sixth arches.

Figure 34.4 Summary – Derivatives of arch cartilages.

LANGMAN’ S MEDICAL EMBRYOLOGY, FIGURES 17.8 AND 17.9.

Figure 34.5 Summary – Muscular derivatives of pharyngeal arches.

THE DEVELOPING HUMAN, FIGURE 9-5.

The fourth and sixth aortic arch arteries give rise to arteries in the thorax. From the right fourth aortic arch comes the proximal part of the right subclavian artery while the left contributes to the development of the arch of the aorta. The sixth aortic arches give rise to the proximal portions of the pulmonary arteries as well as the embryonic ductus arteriosus.

Figure 34.6 Growth of 2nd arch caudally provides for a smooth lateral neck contour. THE DEVELOPING HUMAN, FIGURE 9-9.

How does the smooth contour of the neck result?

As you might have noticed, fully developed humans don’t have swellings in their necks with clefts between them. How is the pharyngeal apparatus transformed to produce the aesthetically pleasing transition between head and shoulders?

During the fifth week, the second arches enlarge and migrate caudally, overgrowing the third and fourth arches. Thesecond arches fuse with the tissues of the upper thorax.

This process covers up and internalizes the second, third, and fourth pharyngeal clefts. Subsequently the three clefts fuse to form bilateral potential spaces in the developing neck called cervical sinuses. Normally the cervicalsinuses collapse and are obliterated.

CLINIC AL APPLIC ATION

In some cases, normal neck development goes awry:

Lateral cervical cysts (aka –

branchial cysts) are fluid- or debris-filled masses that develop from persistent cervical sinuses. Thesepresent in the neck along the anterior border of the sternocleidomastoid muscle.

Find a mass along the anterior border of the SCM in the neck of a youngster or pre-teen?

Think lateral cervical cyst.

Figure 34.7 Lateral cervical cyst.

Branchial sinuses are small canals that open onto the lateral neck along the anterior border of the sternocleidomastoid (external branchial sinus) or into the pharynx near the tonsillar fossa (internal branchialsinus). These result from incomplete closure of the cervical sinus laterally as the 2nd arch grows caudally over the3rd and 4th arches (external sinus) or rupture of the second pharyngeal membrane (internal sinus). If the sinusconnects internally to a lateral cervical cyst, the sinus may “weep” fluid onto the neck surface.
A branchial fistula is a rare tract or small canal that has two openings: one external and one internal. The external opening is usually along the anterior border of the sternocleidomastoid and the internal opening is near the tonsillar fossa.

Figure 34.8 Fates of pharyngeal pouches. LANGMAN’ S MEDICAL EMBRYOLOGY, FIGURES 17.10 AND 17.11.

A fistula has two openings, a sinus has one opening, and a cyst is a closed sac containing a liquid or semisolid materialwithout any openings.

Phar y ngeal pouches

The endoderm of the pharynx lines the internal aspect of the pharyngeal arches and forms a series of diverticula that protrude outward between the arches. These are the pharyngeal pouches.

The pouches internally and clefts externally are separated by the pharyngeal membranes.
Four pouches develop, numbered from cranial to caudal:

first, second, third, and fourth.

The third and fourth pouches each develop dorsal and ventral processes.
The pouches grow and expand away from the pharynx. The first and second pouches retain their internal connections to the pharynx, while the third and fourth pouches detach and form structures distant from the pharynx.

Pharyngealpouch	Definitive structures
First	Tympanic cavity and pharyngotympanic(Eustachian tube) Take note that the Eustachian tube is connected to the nasopharynx
Second	Tonsillar fossa Later, mesenchyme invades the fossa toform the palatine tonsil. The tonsillar fossa is in the lateral wall of the oropharynx.
Third	Dorsal process = Inferior parathyroid gland Ventral process = Thymus
Fourth	Dorsal process = Superior parathyroid gland Ventral process = Parafollicular cells (C-cells) of thyroid gland The ventral process of the fourth pouch is often referred to as the ultimobranchial body. Some embryologists claim it to be a 5th pouch instead (ultimo translates to “last”, so it is the last pouch to form and that makes it the caudal-most pouch). Regardless of its classification, itgives rise to the parafollicular cells, whichmake the hormone calcitonin.

Figure 34.9 Adult derivatives of pharyngeal pouches. THEDEVELOPING HUMAN, FIGURE 9-8.

The paradox of the parathyroid glands: Why is it that the definitive inferior parathyroid glands, which are topographically below the superior parathyroid glands, are derived from the third pharyngeal pouches, which start out cranial to the fourth pouches, the pouches that give rise to thesuperior glands? Ponder this.

Recall that endoderm of the third pouches also gives rise to the thymus, an organ of the thorax. The caudal descent of the third pouch endoderm apparently carries the future inferior parathyroid glandbelow the migrating the fourth pouch endoderm, flip-flopping their before and after locations.

Phar y ngeal cleft s

The first pharyngeal clefts give rise to the external acousticmeatuses. These transmit sound waves into the head. The second,third, and fourth pharyngeal clefts are overgrown by the second pharyngeal arch when the smooth neck forms. Subsequently, theyfuse to form the cervical sinus (discussed earlier), a potential space that normally obliterates later in development.

Phar y ngeal membr anes

The membranes are located where ectoderm-lined pharyngeal clefts areadjacent to the endoderm-lined pharyngeal pouches. Normally there is a layer of mesoderm interposed between the cleft and pouch, making the membrane a trilaminar structure.
The first pair of pharyngeal membranes gives rise to the tympanic membranes

(eardrums).

Obliteration of the 2nd, 3rd, and 4th clefts along with growth andmigration of the 3rd and 4th pouches eliminates the other pharyngealmembranes = they do not form any definitive adult structures.

Hint: Don’t overlook this short chapter. Since many head and neck defectsare due to faulty development of the pharyngeal apparatus, Boards examsusually include questions on this topic!

De velop ment of the fa ce and par otid gl and

The face develops from five ectoderm-covered and mesenchyme-filled primordial structures: a single frontonasal prominence and left and right maxillary and mandibular prominences. These grow and converge around the primitivemouth (stomodeum).

Frontonasal prominence – develops cranial to the developing brain. The embryonic head fold brings it down in thecenter of the developing face. The ophthalmic division of trigeminal (V1) innervates it.
At its caudal end, ectoderm invaginates to form left and right nasal pits. Mesenchyme in the frontonasal prominencepiles up around the pits to form medial and lateral nasal prominences.
The medial nasal prominences fuse: the upper portion forms the dorsum of the nose and nasal septum; the lower portion forms the intermaxillary segment, which gives rise to the philtrum of the upper lip and the primary palate= the triangular region of the palate anterior to the incisive foramen – which includes the upper incisor teeth.
Maxillary prominences develop from the first pharyngeal arch. They give rise to the upper jaw and are innervated by the maxillary nerve (V₂).
Fusion of the maxillary prominences with the lateral nasal prominences gives a smooth transition from the side of the nose to the cheek.
Fusion of the maxillary prominences with the intermaxillary segment completes the upper lip.

Figure 34.10 Normal development of lip and palate. LANGMAN’ S MEDICAL

EMBRYOLOGY, FIGURE 17.28.

Mandibular prominences also develop from the first arch and are innervated by the mandibular nerve (V₃). They give rise to the lower jaw. They fuse below the mouth to complete the lower lip and chin.
The parotid gland is formed by invagination of facial

ectoderm in the cleft between the maxillary and mandibular prominences. The ectoderm pinches oﬀ from the surface ofthe face, but maintains a connection (future parotid duct) to the angle of the wide embryonic mouth. As the mouth size is reduced, the duct loses it connection to the angle of the mouth, but retains its connection to the oral cavity, now opening opposite the 2nd upper molar.

Figure 34.11 LANGMAN’ S MEDICAL EMBRYOLOGY, FIGURES 17.22 AND 17.23.

CLINIC AL APPLIC ATION

CO N G E N I TA L D E F E C T S O F T H E FA C E

Incomplete or partial fusion of the facial prominences results in facial clefts. These are the most common craniofacial anomalies.

Cleft lip is the most common facial cleft. It is caused by failure of the maxillary prominences to fuse properly with the intermaxillary segment (fused medial nasal prominences) along the edge of

Figure 34.12 A = Unilateral cleft of lip; B= Unilateral cleft of lip and anterior palate; C = Bilateral cleft of lip and anterior palate. LANGMAN’ S MEDICAL EMBRYOLOGY,

FIGURE 17.28.

the philtrum. Underdevelopment of mesenchyme due to deficiencies in neural crest cell migration andproliferation is thought to be the reason. The degree of clefting is variable – from small notches in the border of the lip to complete separation of the lip and underlying bone.

Underdevelopment of the first pharyngeal arch can lead to varied malformations of the face. First archsyndrome is

a collection of genetic malformations involving derivatives of the maxillary and mandibularprominences. These may include underdevelopment of the mandible or zygomatic bones, enlargement of the mouth, and malformations of the eyelids, ears, or palate. It appears that a failure of proliferation of neural crest cells may be the underlying factor.

Treacher Collins syndrome is a well-known manifestation of first arch syndrome.

De velop ment of the th y r oid gl and

The butterfly-shaped thyroid gland originates as a diverticulum of endoderm that grows caudally in the midline from the floor of the primitive pharynx. It is not part of the pharyngeal apparatus (described earlier). As it grows caudally it acquires a bi-lobed morphology. By the 7th week of development it has descended in front of the hyoid bone and future larynx to itsfinal position anterior to the trachea. After descent, it remains connected to the floor of the pharynx by a collapsed tube of endoderm called the thyroglossal duct.

Proximally, the location of the thyroglossal duct within the oral cavity is indicated by the foramen cecum in the fully developed tongue.

The thyroid begins to function in the fetus. Follicular cells in the thyroid that manufacture thyroid hormone are derived from the endoderm of the thyroid diverticulum.

Parafollicular cells (“C”-cells) in the thyroid that produce calcitonin are derived from the endoderm of the ventral part of the 4th pharyngeal pouch (also known ultimobranchial body). This was described earlier in this chapter.

Figure 34.13 LANGMAN’ S MEDICAL EMBRYOLOGY, 12TH ED., FIGURE 17.18.

CLINIC AL APPLIC ATION

Figure 34.14 LANGMAN’ SMEDICAL

EMBRYOLOGY, 12TH ED.,FIGURE 17.20.

The thyroglossal duct normally closes and atrophies. If it doesn’t,it provides a potential space for a cyst to develop within. Thyroglossal duct cysts can occur anywhere along the route of the thyroglossal duct – but most occur near the hyoid bone.They account for up to 70% of congenital neck masses. They present as round, painless swellings in the midline of the anterior neck and classically elevate when the tongue is protruded.When infected they become red, painful lumps. Thyroglossal duct cysts are removed by surgical excision of the cyst, the thyroglossal duct tract, and the central portion of the hyoid bone (this is called the Sistrunk procedure). This somewhat radical procedure greatly reduces the likelihood that the cyst will recur.

When diagnosing a thyroglossal duct cyst is important to rule out another diagnosis = ectopic thyroid. Ectopic thyroid tissue canbe found anywhere along the course of the thyroglossal duct.Thyroid tissue occurring near the

foramen cecum is known as a lingual thyroid. Accessory thyroid tissue that projects upwards from theisthmus of the thyroid is a common variation – this tissue is known as a pyramidal lobe of the thyroid gland. Ectopic thyroid is histologically and functionally normal thyroid tissue.

CHAPTER SUMM AR Y

After studying this chapter, you should be able to describe thedevelopment/ tissue sources of these structures:

VIDEOS: TYING IT ALLTOGETHER

Pharyngeal apparatusdevelopment, tongue, and thyroid gland (with dramatic music!).

Development of face andpalate.

Muscles of mastication

Muscles of facial expression
Stylopharyngeus muscle
Muscles of the larynx and pharynx
Muscles of the soft palate
Muscles in the tympanic cavity
Mylohyoid and digastric muscles
Bones of the upper jaw
Bones of the lower jaw
Auditory ossicles
Styloid process
Hyoid bone
Common carotid arteries
Ductus arteriosus
External acoustic meatus
Pharyngotympanic tube
Tympanic cavity
Tympanic membrane

Tonsillar fossa
Parathyroid glands
Thyroid gland (follicular and parafollicular cells)
Thymus
External nose
Nasal septum
Philtrum and primary palate
Upper lip
Lower lip
Parotid gland and duct

The development of the tongue and palate are covered in the chapter on the oral region (chapter 36). The development of the nasal cavities and paranasal sinuses are coved in chapter 37.

35

Temporal and infratemporal regions; temporomandibular joint

OPTIONAL READING

Clinically Oriented Anatomy, 7th ed., Temporomandibular joint section through Arthritis of TMJ.

CHAPTER CONTENT S TEMPOR AL REGION

INFR ATEMPOR AL REGION

Bony anatomy Muscles of mastication

Summary: Movements of the mandible

NER VES OF THE INFR ATEMPOR AL FOSSA

Mandibular division of trigeminal nerve (V3)

Sensory branches of V3 Motor branches of V3

Chorda tympani nerve Otic ganglion Parasympatheticfibers

Posterior superior alveolar nerves

Blood vessels of the infratemporal fossa

Maxillary artery Branchesto the ear

Branches tomeninges and skull Branches to teeth

Branches to muscles

Branches to the palate andnasal cavity Pterygoid venous plexus Sphenomandibular ligaments Temporomandibular joint (TMJ)

General features ofsynovial joints Anatomy of the TMJ

Temporal and infratemporal regions; temporomandibular joint

Tempor al region

The temporal fossa is the sunken area located onthe lateral skull above the zygomatic arch.

Its floor contains portions of the frontal,parietal, temporal, and sphenoid bones.
The upper boundary is the curved superior temporal line.

The inferior boundary is the zygomatic arch.

Contents: The temporal fossa is occupied by the temporalis muscle and its fascia, nerves, and vessels.

Origin: Temporalis arises from the bony floor of the fossa and from the deep surface of the stout temporal fascia, which covers the muscle externally. The temporal fascia attaches above to the superior temporal line and below to the zygomatic arch. The scalp is external to the fascia.
Insertion: The muscle fibers are arranged like it fan. They converge below on a tendon that attaches to the coronoid process of the mandible.

Figure 35.1 Attachments of temporal fascia. GRAY’ S ANATOMY FOR STUDENTS, FIGURE 8.138.

Actions: Temporalis is a chewing muscle. Its vertical fibers elevate the mandible to close the jaw. The horizontal fibers retract the mandible after it has been protruded.
Nerves and vessels: The deep temporal nerves (from V₃) and deep temporal arteries (from the maxillary artery) enter the deep surface of the muscle, passing upward between the muscle and the bony floor of the temporal fossa.

Figure 35.2 GRAY’ S ANATOMY FOR STUDENTS, FIGURE 8.139.

Infr atempor al region

The infratemporal fossa (ITF), as its name implies, is located inferior tothe temporal bone and temporal fossa. It is wedge-shaped; wider at the topand tapered at the bottom. The infratemporal fossa is not easily visualizedexternally since it is located deep to the masseter muscle and ramus of themandible.

Bony anatomy

Imagine the infratemporal fossa as a bony box, tipped upside-down, with its lid open. We will begin our discussion with an empty box, and then addits contents. The boundaries of the ITF are:

Lateral = ramus of mandible.
Medial = lateral surface of the lateral pterygoid plate (sphenoidbone). The pharynx is also in the medial wall.
Anterior = posterior surface of the body of the maxilla.
Posterior = tympanic plate (the shelf of bone below theexternal acoustic meatus) and styloid process – both are parts of the temporal bone.
Superior = infratemporal surface of the greater wing of the sphenoidbone. The gap deep to the zygomatic arch connects the infratemporalfossa to the temporal fossa above. It is filled with the temporalis muscle.
Inferior = has no bony boundary – it is closed by the attachment ofthe medial pterygoid muscle to the mandible.

Boundaryof ITF	Opening	Communicateswith . . .	Contents
Roof	Foramen ovale	Middle cranialfossa	V₃ Lesserpetrosalnerve Accessorymeningeal artery (if present)
Roof	Foramen spinosum	Middle cranialfossa	Middlemeningealartery
Medialwall	Pterygomaxillary fissure	Pterygopalatinefossa	Maxillary artery Posterior superior alveolarnerves (V₂)
Anteriorwall	Inferior orbital fissure	Orbit	Infra-orbitalartery
Lateralwall	Mandibular notch	Face	Massetericnerve and vessels

The bony box has openings through which the ITFcommunicates with other regions of the head. It’s fun to spend some time with your skull and locate these openings with a pipe cleaner. You should know the structures that pass through each of these openings:

Figure 35.3 CLINICALLY ORIENTED ANATOMY,

FIGURE 7.67. Figure 35.4 CLINICALLY ORIENTED ANATOMY, FIGURE 7.67.

Muscles of mastication

There are four chewing (mastication) muscles: one in the temporal fossa (temporalis), one on the face (masseter) and twoin the infratemporal fossa (medial and lateral pterygoid).

All are derived from the mesenchyme of the embryonic

first pharyngeal arch.

All are innervated by the only branch of the trigeminal nerve that carries motor fibers = the mandibular nerve (V₃).
All receive their blood supply from the maxillary artery.

Temporalis: described earlier with the temporal region.

Masseter: located on the face and largely covered by the parotid gland.

Origin: its two heads arise from the zygomatic bone and zygomatic arch
Insertion: external surface of ramus of mandible
Action: elevates the mandible to close the jaw and clench the teeth
Innervation: masseteric nerve from V₃

Figure 35.5

Figure 35.6 NET TER, ATLAS OF HUMAN ANATOMY, PLATE 49.

Medial pterygoid muscle: quadrangular muscle within the ITF that slopes medial to lateral as well as anterior to posterior. It is essentially the mirror image of the masseter muscle, but on the internal surface of the mandibular ramus(the masseter is on the external surface).

Origin: arises as two heads, one from the maxilla and one from the medial surface of the lateral pterygoid plate (sphenoid bone).
Insertion: medial surface of ramus of mandible.
Action: elevates the mandible and helps protrude it.
Innervation: branch of V₃

Lateral pterygoid muscle: triangular muscle in the ITF = broad at its origin, tapers at its insertion.

Origin: like the medial pterygoid, it has two heads. The upper head arises from the greater wing of the sphenoidbone (roof of ITF), while the lower head arises from the lateral surface of the lateral pterygoid plate.
Insertion: the two heads converge and attach to the neck of the mandible (just below the condyle) and to the capsule of the temporomandibular joint.
Action: protrudes the mandible, an action necessary for any substantial opening of the mouth.
Innervation: branch of V₃.

Figure 35.7

ANATOMY FOR STUDENTS, FIGURE 8.136.

Summary: Movements of the mandible

These occur at the temporomandibular joint (TMJ).

Three muscles (temporalis, masseter, and medial pterygoid) can elevate the jaw and clench the teeth. This explains the power generated for biting.
Because of the direction in which chewing muscles attach to the mandible, the jaw can be deviated medial and lateral while being elevated and depressed. Synchronized action of the muscles can thus produce the motions needed for grinding food on the teeth.
The buccinator muscles (muscles of facial expression) assist with chewing by compressing the cheeks to keep food on the teeth.
Gravity helps with opening the mouth (depressing the mandible) when the head is upright. Suprahyoid muscles (geniohyoid, mylohyoid, digastric), located below the chin, are recruited to assist with depressing and retracting the mandible when there is resistance to such movements – i.e., when gravity can’t help.

Ner ves of the infr atempor al fossa

Mandibular division of trigeminal nerve (V₃)

As it leaves the trigeminal ganglion in the middle cranial fossa, V₃consists of a large sensory root and a smaller motor root. The roots pass separately through foramen ovale and fuse just below it. The main trunk of the nerve is deep to the lateral pterygoid muscle. Anatomy textsdescribe V₃ as separating into anterior and posterior divisions within theITF. This can’t be seen very well in the lab, so we will simply classify themajor branches of V₃ as sensory or motor. The branches leave V₃ high in the ITF, just below foramen ovale. Their origins can only be seen by removing the lateral pterygoid muscle.

Sensory branches of V₃

Buccal nerve – passes downward and forward, adjacent to and sometimes within the tendon of temporalis. It supplies the check – both the skin outside and mucous membrane inside. [NOTE: don’tconfuse this nerve with the motor buccal branch of the facial nerve!]
Lingual nerve – heads toward the oral cavity sandwiched between the medial pterygoid muscle and ramus of the mandible. Transmitsgeneral sensation from the anterior 2/3 of the tongue, floor of the mouth (sublingual area), and the lingual sides of the lower gums(gingivae). The chorda tympani nerve joins the lingual in the ITF. Thus the lingual nerve also carries preganglionic parasympathetic fibers (to the submandibular and sublingual glands) and taste fibers from the anterior 2/3 of tongue.

Inferior alveolar nerve – enters the mandibular foramen and traverses the body of the mandible via themandibular canal. Transmits general sensation from the lower teeth. The mental nerve, a branch of the inferior alveolar, supplies the skin of the lower lip and chin via the mental foramen.
Auriculotemporal nerve – leaves V₃ as two trunks that encircle the middle meningeal artery and fuse lateral to it. Passesdeep to the condylar process of the mandible and the parotid gland, ascends on the face anterior to the auricle, and then enters the scalp. Transmits general sensations from the scalp, auricle, and temporomandibular joint. It carriespostganglionic parasympathetic fibers from the otic ganglion that innervate the parotid gland.

Motor branches of V₃

Nerve to tensor veli palatini muscle (a muscle of the soft palate).
Nerve to tensor tympani muscle (in the tympanic cavity).

• Nerves to medial and lateral pterygoid muscles

Masseteric nerve
Deep temporal nerves (anterior and posterior – to the temporalis muscle)
Nerve to mylohyoid and anterior belly of digastric – hitches a ride with the inferior alveolar nerve, branching fromit just before it enters the mandibular foramen.

Figure 35.8

Figure 35.9 Branches of V₃ shown after removal of lateral pterygoid muscle. CLINICALLY ORIENTED ANATOMY, FIGURE 7.74.

Figure 35.10 GRANT ’ S ATLAS OF ANATOMY, 13TH ED., FIGURE 7.52.

Chorda tympani nerve

From Cranial nerve VII, it carries taste fibers from the anterior 2/3 of the tongue and visceral motor (parasympathetic) fibers to the submandibular ganglion. Chorda tympani enters the ITF from the tympanic cavity through the petrotympanic fissure – a tiny crack in the temporal bone just anterior to the temporomandibular joint. It joint the lingual nerve high in the infratemporal fossa.

Otic ganglion

One of the four parasympathetic ganglia of the head, it is located in the ITF attached to the medial side of the mandibularnerve just inferior to foramen ovale. Preganglionic parasympathetic fibers from the lesser petrosal nerve (CN IX) synapse on postganglionic cell bodies in the otic ganglion. Lesser petrosal enters the ITF through foramen ovale.

Postganglionic fibers travel with the auriculotemporal nerve to their destination: the parotid gland.

Parasympathetic fibers

The pathways of innervation of the three major salivary glands traverse the infratemporal fossa. They originate in cranial nerves VII (submandibular and sublingual glands) and IX (parotid gland), but finish their journeys as postganglionic parasympathetic fibers hitching rides on branches of the V₃ in the ITF (lingual and auriculotemporal nerves). Synapses between pre-G and post-G neurons occur at the submandibular and otic ganglia. The pathways of innervation are sketched out in flow charts in chapter 36: The oral region and pharynx.

Figure 35.11 GRAY’ S ANATOMY FOR STUDENTS, FIGURE 8.146.

Posterior superior alveolar nerves Branches of the maxillary nerve (V₂), they pass out of the pterygopalatine fossa via the pterygomaxillary fissure. In the ITF, they pass along the posterior surface of the maxilla and enter it viatiny foramina. These nerves carry sensation from the upper molar teeth and their gingivae and from the mucosa of the maxillary air sinus.

Blood vessels of the infratemporal fossa

Maxillary artery

One of two terminal branches of the external carotid artery (what is the other one?), it enters the ITF from the parotid gland by passing deep to the condylar process of the mandible. It is intimately associated with the lateral pterygoid muscle. In about 50% of cases it passes superficial tothe muscle, while in the other 50% it passes deep to the lower head of the muscle.

This artery can be a toughie for several reasons: it is diﬃcult to dissect(tough fascia and often hidden by the lateral pterygoid muscle), has many branches (some quite small), and it disappears from view rather quickly as it enters the pterygopalatine fossa via the pterygomaxillary fissure. Afavorite textbook of your professor labels this artery as “the bane of the medical student”! Realistically, medical students have many banes, so we will simplify the maxillary artery by placing its branches into a few categories.

Keep in mind that this scheme does not organize arteries in thetopographic order in which they branch. Consult your Atlas.

Branches to the ear

Deep auricular and anterior tympanic arteries supply the external acoustic meatus and tympanic cavity, respectively. Very small. Wewon’t see these in lab.

Branches to meninges and skull

Middle meningeal artery: super-important branch that enters thecranial cavity via foramen spinosum. It supplies blood to the periosteum, bones, and dura associated with the calvaria (skull cap).
Accessory meningeal artery: not too important and often absent. Enters the cranial cavity via foramen ovale to supply dura in the floorof the middle cranial fossa.

Branches to teeth

Inferior alveolar artery: Follows the nerve of the same name into the

mandibular foramen and mandibular canal where it supplies the lower teeth.

Posterior superior alveolar artery: Its small branches follow thenerves of the same name into the maxilla, supplying the posteriormolar and premolar teeth and maxillary air sinus.
Infra-orbital artery: enters the orbit via the inferior orbital fissure.It supplies a few extra-ocular muscles in the orbit and a small portion of the central face, but perhaps its most important job is to supply the upper incisor and canine teeth.

Branches to muscles

Deep temporal (temporalis),

masseteric, and pterygoid arteries.

Buccal artery to cheek and buccinator muscle

Branches to the palate and nasal cavity

Descending palatine and sphenopalatine arteries – these arise from the maxillary artery within the pterygopalatine fossa, so we won’t describe them here. These arteries can be considered the terminal branches of the maxillary artery.

Figure 35.12 Branches of the maxillary artery. Anatomists and clinicians divide the artery into three parts. The first two(mandibular and pterygoid parts) give oﬀ branches in the infratemporal fossa. GRANT ’ S ATLAS OF ANATOMY, 13TH ED.,FIGURE 7.51.

Pterygoid venous plexus

This network of small veins courses through the fascia in the ITF and surrounds the lateral pterygoid muscle. A short maxillary vein drains the plexus, joining the superficial temporal vein within the parotid gland to form the retromandibular vein. Tributaries of the pterygoid plexus drain structures that are supplied by the maxillary artery. It hasclinical importance as a “go-between”, connecting veins of the face with the cavernous sinus. This route, along with a routethrough the orbit (ophthalmic veins – described with the face), provides a possible way for infections to pass from face to cranial cavity.

Sphenomandibular ligaments

Located on each side of the head within the infratemporal fossae, they attach above to the inferior surface of the sphenoid bone near the foramen spinosum and below to the lingula of the mandible, a bony spine near the mandibular foramen. Just above this, the inferior alveolar nerve is sandwiched between the ligament and mandible. These are thought to function as asupports for the lower jaw and as check ligaments to prevent excessive movements of the TMJ.

Figure 35.13 GRAY’ S ANATOMY FOR STUDENTS, FIGURE 8.148.

Figure 35.14 GRAY’ S ANATOMY FOR STUDENTS, FIGURE 8.143.

Temporomandibular joint (TMJ)

The TMJ is the largest and most clinically important synovial joint inthe head. Before we consider the TMJ, let’s lay out the features allsynovial joints possess, since we haven’t learned about them yet.

General features of synovial joints

Articular (joint) capsule: A tough layer of dense connective tissue that joins together the articulating bones, allowing them to moverelative to one another without being pulled apart.
Articular (joint) cavity: within the joint capsule, it containslubricating fluid and provides the space for the bones to move.
Articular cartilage: the articular surfaces of bones within synovialjoints are line by hyaline cartilage. It resists and distributes compressive forces.
Synovial membrane: loose connective tissue lining the inside ofthe articular capsule and richly supplied with blood vessels. It produces synovial fluid.
Synovial fluid: “Joint Oil” – a viscous fluid resembling egg white(ovia = Latin for “egg”) that lubricates the joint surfaces and providesnutrients. It is nature’s “WD-40”.
Ligaments – located around the joint capsule, they further reinforce the joint.
A small number of synovial joints (knee and TMJ for example)contain one or more articular discs (menisci). These are shelves of fibrocartilage within the joint cavity. They are thought to add cushioning and allow for complex joint movements, such ascombinations of rotation and forward/backward gliding.

Anatomy of the TMJ

The temporomandibular joint is the articulation between the condyle of the mandible and the mandibular fossa of the temporal bone. The condyle is elliptical in shape, having its long axis oriented from medial to lateral.
Anterior to the mandibular fossa is a rounded eminence on the inferior margin of the zygomatic arch called the articulartubercle. It restricts excessive anterior movement of the mandible and possible dislocation of the joint.
The articular capsule of the TMJ is attached around the edge of the mandibular fossa, to the articular tubercle, and to the neck of the mandible just below the condyle.
The TMJ is diﬀerent from most synovial joints in that the articular cartilage is

fibrocartilage, not hyaline cartilage.

The TMJ has an articular disc (called the meniscus by clinicians) situated in the center of the joint space. Itattaches to the entire circumference of the joint capsule, dividing the joint space into two joint cavities: upperand lower joint spaces.
The lateral pterygoid muscle inserts into the TMJ capsule and to

the neck of the condylar process. When the muscle contracts, both the mandible and TMJ capsule move forward. Since the articular disc attaches to the joint capsule, it too moves forward when the mouth opens.

Figure 35.16 CLINICALLY ORIENTED ANATOMY, FIGURE 7.69.

The auriculotemporal nerve and the superficial temporal artery supply the TMJ.

Figure 35.15 CLINICALLY ORIENTED ANATOMY, FIGURE 7.69.

Figure 35.17 Normal (left) and anteriorlydisplaced (right) articular disc. IMAGES ANDANIMATIONS FROM HT TP://

TMJTREATMENT.COM.AU/WHAT-IS-TMJ- OR-TMD/.

CLINIC ALAPPLIC ATION TMJ DYS F U N C T I ON

Trivia Night in the Anatomy Lab:

Every time you swallow, your molarteeth come in contact (try it and see).
During this contact about 25 poundsof pressure is placed on the teeth. Much of this pressure is transferred to the TMJ. It’s no wonder that TMJ dysfunction is common.

Movie 35.1 Displacement of the articular discdemonstrated in cadaver specimens: “Yoint Video” from Sweden.

JOINT CLICKING

Technically known as internal derangementof the TMJ. Joint clicking occurs when the articular disc becomes displaced anterior to the mandibular condyle when the mouth is opened (anterior displacement of the disc). If the displaced articular disc returns to its normal place as the mouth is opened wider, the patient will feel a “pop” and hear a “click”.This is called anterior displacement with reduction. If the articular disc remains displaced throughout the entire range of joint motion, the displacement is without reduction. These patients cannot fully open their mouths.

Figure 35.18 FROM LUYK NH, LARSEN PE: THEDIAGNOSIS AND

TREATMENT OF THE DISLOCATED MANDIBLE. AMJ EMERG MED 1989; 7:329.

CLINIC ALAPPLIC ATION TMJ D I S LO C AT I ON

When the mouth is widely opened (as in yawning during

VIDEO

Check out this emergency departmentvideo: Reducing the dislocated jaw.

an anatomy lecture), the mandibular condyle and articular disc are precariously perched on the articular tubercle. A sudden contraction of the muscles that open the mouth, or a slap on the back from your classmate, could pull thearticular disc and mandibular condyle over theedge of the prominence into the infratemporalfossa. Once there, the masseter and medial pterygoid muscles may spasm and clamp down on the dislocated

mandible like a vise. The patient comes into the Emergency Department with his or her mouth stuck open. The dislocation is reduced by pulling the mandible downwardwith the thumbs (heavily wrapped in gauze) to clear the articular tubercle, then giving it a backward push to click it into place.

38

Pterygopalatine fossa

OPTIONAL READING

Clinically Oriented Anatomy, 7th ed., Pterygopalatine fossa section through The bottom line: Pterygopalatine fossa.

CHAPTER CONTENT S

PTER YGOPAL ATINE FOSSA BON Y BORDERS

CO M M U N I C AT I O N S

CO N T E N T S O F T H E P P F O S S A

Pterygopalatine ganglion Maxillary nerve (V2) Maxillary artery

Pterygopalatine fossa

The pterygopalatine fossa (PPF) is a small, bilateral bony spaceimmediately behind the maxilla. Shaped like an inverted teardrop, it is about the size of a thumbnail.

Bon y borders

Anterior = posterior surface of maxilla.
Posterior = anterior surface of the pterygoid process of sphenoidbone (the strut of bone from which the medial and lateral pterygoid plates project).
Medial = perpendicular plate of the palatine bone.
Lateral = open to the infratemporal fossa via the pterygomaxillary fissure.
Superior = body of the sphenoid bone (contains sphenoidal sinuses).
Inferior = the anterior and posterior walls slope towards each other inferiorly, but don’t quite meet. The gap creates the palatine canalwhich descends from the PPF to the palate.

Co m m u n i c at i o n s

The pterygopalatine fossa is small, but mighty; it communicates with manyregions of the head via bony passageways that open on its walls:

Wall ofPPF	Name of opening	Communicates with . . .	Contents
Anterior	Inferior orbital fissure	Orbit	Infra-orbital nerve of (V₂) and artery Zygomatic nerve of (V₂)
Posterior	Formen rotundum	Middle cranial fossa	Maxillary nerve (V₂)
Posterior	Pterygoid (Vidian)canal	Middle cranial fossa via foramen lacerum	Nerve of pterygoid canal (Vidian nerve) Artery of pterygoid canal
Medial	Sphenopalatine foramen	Nasal cavity	Sphenopalatineartery Nasopalatine nerve of (V₂)
Lateral	Pterygomaxillary fissure	Infratemporal fossa	Maxillary artery Posterior superior alveolar nerve of (V₂)
Floor	Palatine canal	Palate, via greater and lesser palatine foramina	Greater and lesser palatine nerves of(V₂) Descending palatine artery

Figure 38.1

CLINICALLY ORIENTED ANATOMY, 7TH ED., FIGURE 7.97.

Co n t e n t s o f t h e p p f o s s a

The contents of this tiny space are three in number: (1) pterygopalatine ganglion (a parasympathetic ganglion introduced earlier in the course), (2) maxillary nerve (V₂) and its branches, and (3) the terminal (third) part of the maxillary artery. As we discuss each of these, it is important to visualize their courses in and out of the PPF through the bony openings we considered above. In lab, use pipe cleaners or wires to simulate the courses of these nerves and vessels.

Figure 38.2 Schematic of PPF showing its connections to other regions of the head. This is a lateral to medial view looking through the pterygomaxillary fissure. CLINICALLY ORIENTED

ANATOMY, 7TH ED., FIGURE 7.98.

Figure 38.3 Anterior view of isolated sphenoid bone.

The anterior surfaces of the pterygoid processes (shown in yellow) form the posterior wall of the PPF. The three bony apertures in the posterior wall can be seen best in this view.

GRAY’ S ANATOMY FOR STUDENTS, 3RD ED., FIGURE 8.150.

Pterygopalatine ganglion

The largest of the four parasympathetic ganglia in the head, it is said tocontain the largest collection of neuron cell bodies in the head outside the brain.

Preganglionic parasympathetic fibers to the pterygopalatine ganglion are supplied by the greater petrosal nerve, a branch of the facial nerve (CN VII). The greater petrosal nerve enters the pterygopalatinefossa through its posterior wall as part of the nerve of the pterygoid canal (Vidian nerve).
The pterygopalatine ganglion contains the cell bodies of postganglionic parasympathetic neurons, whose axons aresecretomotor to the lacrimal gland, nasal glands, and glands of the hard and soft palates and nasopharyx. These fibers reach their targets by hitching rides on branches of V₂.
The nerve of the pterygoid canal is a composite nerve consisting of two parts:
Postganglionic sympathetic fibers (deep petrosal nerve) whose cell bodies are in the superior cervical ganglion. These fibers reach the pterygoid canal by ascending along the internal carotid artery in the carotid canal as part of the carotid plexus. Once in the PPF,they are distributed to glands and blood vessels via branches of V₂.
Preganglionic parasympathetic fibers (greater petrosal nerve) –these fibers leave the genu of the facial nerve in the temporal bone, traverse the floor of the middle cranial fossa under the dura, descend in foramen lacerum, and join the fibers of the deep petrosal nerve at the posterior opening of the pterygoid canal.

The greater petrosal nerve also probably carries taste fibers from taste buds on the palate. These special sensory fibers reach the greater petrosal nerve by first ascending from the palate in palatine branches of V2 and then passing through or around the pterygopalatine ganglion. They have cell bodies in the geniculate ganglion of CN VII.

Nerve of pterygoid canal = Greater petrosal nerve + deep petrosal nerve.

Figure 38.4 Formation of the nerve of the pterygoid canal.

GRAY’ S ANATOMY FOR STUDENTS, 3RD ED., FIGURE 8.153.

Maxillary nerve (V₂)

As described earlier in our little chat on cranial nerves, V₂ carries sensory fibers from the midface and cheekbones, lower eyelids, upper teeth and gingivae, maxillary sinus, palate, nasopharynx, and the mucosa in the posterior-inferior nasal cavity (lateral nasal wall and septum). To reach these areas, V₂ first enters the pterygopalatine fossa via the foramenrotundum. Within the fossa, V₂ is connected to the pterygopalatine ganglion. Several of the branches of V₂ that originate in the PPF pass through the ganglion first, but their nerve fibers do not synapse within it.

Nerves that originate directly from V₂ within the pterygopalatine fossa:

Posterior superior alveolar nerves – pass through the pterygomaxillary fissure, skirt the infratemporal fossa, and penetrate the body of the maxilla. They carry sensation from the maxillary sinus,upper molar and premolar teeth, and their gingivae.
Ganglionic branches (2) – connect to the pterygopalatine ganglion (the

ganglion appears to hang from V₂ by these tiny supports). Sensorynerve fibers from the palate, nasopharynx, and nasal cavities reach V₂through the ganglionic branches. Also, postganglionic parasympatheticand sympathetic nerve fibers leave the pterygopalatine ganglion andjoin V₂ through the ganglionic branches.

Zygomatic nerve – enters the orbit via the inferior orbital fissure.Passes along the lateral wall of the orbit and divides into zygomaticofacial and zygomaticotemporal nerves, which supply the face and “temple” regions, respectively.

Infra-orbital nerve – essentially the continuation of V₂ as it leaves the PPF and enters the orbit via the inferior orbital fissure. In the floor of the orbit the

infra-orbital nerve occupies a groove which guides it into the infra-orbital canal, which then transmits the nerve onto the midface through the infra-orbital foramen. Anterior and middle superior alveolar nerves that supply the upper incisor and canine teeth branch from the infra-orbital nerve.

The following nerves are sensory branches of V₂ that pass through the pterygopalatine ganglion, thus appearing to beconnected to the ganglion itself.

Pharyngeal nerve – sensory to the upper nasopharynx.
Greater and lesser palatine nerves – sensory to the hard and soft palates, respectively. They descend in the palatinecanal as two separate nerves, then reach their targets through the greater and lesser palatine foramina.
Posterior lateral nasal nerves supply the mucosa of the posterior lateral nasal wall (conchae and meatuses). Some branch directly from the pterygopalatine ganglion, while others are derived from the palatine nerves as they descend in the palatine canal.
Nasopalatine nerve – passes through the sphenopalatine foramen, hops across the sphenoid bone, and then passesobliquely forward across the nasal septum. It is sensory to a good portion of the nasal septum, then sends it terminal portion through the incisive fossa to supply the anterior part of the hard palate and gums, behind the upper incisor teeth

Figure 38.5 Branches of V₂ in PPF.

CLINICALLY ORIENTED ANATOMY, 7TH ED., FIGURE 7.98.

Concerning ALL of the branches of V₂:

They carry both sensory and autonomic fibers.
Sensory neurons have cell bodies in the trigeminal ganglion.
Parasympathetic neurons (postganglionic) have cell bodies in the pterygopalatine ganglion.
Sympathetic neurons (postganglionic) have cell bodies in the superior cervical ganglion.

Figure 38.6 Diagrams showing sensory and autonomic pathways in branches of V₂. CLINICALLY ORIENTED ANATOMY, 7TH ED., FIGURE 7.100.

Maxillary artery

The tale of the maxillary artery has already been told = it arises as one of the two terminal branches of the external carotid artery and most of its course is through the infratemporal fossa. Upon reaching the pterygomaxillary fissure, the tail end of the maxillary artery enters the pterygopalatine fossa. Anatomists refer to this as the third (or pterygopalatine) part of the artery. It produces four or five branches within the PPF, but we will only dwell on the important ones here:

Infra-orbital artery – enters the orbit via the inferior orbital fissure with the nerve of the same name. Supplies thefloor of the orbit, the inferior rectus and inferior oblique muscles, and the midface.
Descending palatine artery – traverses the palatine canal and near its inferior end divides into greater and lesser palatine arteries, supplying the hard and soft palates, respectively, through their corresponding foramina.
Sphenopalatine artery – a large artery that is essentially the continuation of the maxillary artery. It is directed mediallythrough the sphenopalatine foramen to enter the lateral wall of the nasal cavity. You will recall that this artery is the primary blood supply to the posterior nasal cavity and that serious epistaxis results if it is damaged.

Figure 38.7 Branches of maxillary artery in PPF. CLINICALLY ORIENTED ANATOMY, 7TH ED., FIGURE 7.98.

VIDEOS: TYING IT ALLTOGETHER

Dr. Acland: Thepterygopalatine fossa and maxillary nerve.

UBC: Pterygopalatine fossatraﬃc analogy.

CLINIC AL APPLIC ATION

PTER YGOPAL ATINE GANGLION AND V ₂ BLOCKS

Blockage of the pterygopalatine ganglion with an anesthetic hasbeen shown to be useful in management of cluster headaches and various types of facial neuralgias that don’t respond to conventional pharmacologic therapy. The preferred approach to the PPF and ganglion is through the nasal cavity. An applicator with anesthetic (or needle if injected) is positioned just posteriorto the middle nasal concha, allowing the anesthetic to diﬀuse through the nasal mucosa into the pterygopalatine fossa via the sphenopalatine foramen.

Dentists who wish to block V₂ often use the intra-oral approach of injecting an anesthetic into the pterygopalatine fossa via the greater palatine foramen and palatine canal. To do this, an angled needle is advanced 25–30 mm up the palatine canal and an anesthetic solution is introduced, flooding the pterygopalatinefossa (sounds worse than having a root canal!). This blocks V₂and numbs all the areas it supplies, allowing the dentist to work on teeth anywhere in the upper quadrants.

WASHINGTON STATE UNIVERSITY

Elson S. Floyd College of Medicine

Gross Anatomy base material 6

Table of Contents

30

Neck fascia and triangles

Sur fa ce fe atures and l andm arks

Muscles of the neck

• Sternocleidomastoid muscle (SCM)

• Trapezius muscle

• Suprahyoid muscles

• Mylohyoid (V3: nerve to mylohyoid);

• Infrahyoid muscles

Neck ly mph atic dr aina ge , brief intr o

Neck fascia

• Deep Cervical Fascia

· Investing fascia

· Pretracheal fascia

· Prevertebral fascia

· Carotid Sheath

• Fascial Spaces

The cer vic al plexus

Motor branches of the cervical plexus

Sensory branches of the cervical plexus

Triangles of the neck

Posterior triangle

Anterior triangle

Submental triangle

Submandibular triangle

Muscular triangle

Carotid triangle

· Contents: Common carotid artery, carotid bifurcation, carotid sinus and carotid body, ansa cervicalis;, deep cervical lymph nodes, internal jugular vein, vagus nerve (X), and hypoglossal nerve

Ov e r v i e w o f c a r ot i d a r t e r i e s i n t h e n e c k

Ov e r v i e w o f i n t e r n a l j u g u l a r v e i n

Ov e r v i e w o f va g u s n e r v e i n t h e n e c k

31

Root of the neck

Root of the neck

Skele tal fr ame w ork

Pre vertebr al muscles in the neck

Blood and ly mph vessels associ ated with the r oot of the neck

Ner ves

• Vagus nerves and Recurrent Laryngeal nerves

Ot h e r o r g a n s

32

Overview of neck viscera; thyroid and parathyroid glands

Overview of neck viscera; thyroid and parathyroid glands

Respir ator y l ay er = l ar y nx and tr a chea

Digestive l ay er = phar y nx and esopha gus

Endocrine l ay er = th y r oid and par ath y roid gl ands

· Pathologies and Congenital Defects

Ly m p h at i c d r a i n a g e o f t h e h e a d a n d n e c k

33

Larynx

Larynx

Func tions of the l ar y nx

Ca r t i l a g e s o f t h e l a r y n x

• Epiglottis

La r y n g e a l c av i t y ( a i r way o f t h e la r y n x )

saccules

Fibr o -el astic membr anes

• Quadrangular membrane

• Conus elasticus

La r y n g e a l m u s c l e s

Inner vation of the l ar y nx ( cn x)

• Recurrent laryngeal

Blood supp ly and

Embr yology of the l ar y nx

Tr a chea

34

Head and neck development

Head and neck development

The phar y ngeal ap par atus

Co m p o s i t i o n o f a p h a r y n g e a l a r c h

Details of the individual pharyngeal arches

First arch

Second arch

Third arch

Fourth and sixth arches

How does the smooth contour of the neck result?

Phar y ngeal pouches

Phar y ngeal cleft s

• Mylohyoid (V₃: nerve to mylohyoid);

Mandibular division of trigeminal nerve (V₃)

Sensory branches of V₃

Motor branches of V₃

Maxillary nerve (V₂)