THE NECK

Anterior triangle & fascia of the neck

Root of the neck; cervicothoracic relations

Pharynx and palate

Prevertebral region

Larynx

THE ANTERIOR TRIANGLE OF THE NECK

Borders of the anterior triangle of the neck (Clemente plate 436 fig. 693; Grant p. 752; Netter 3e 24, 4e 28)

are formed by the:

• median line of the neck from chin to manubrium;
• anterior margin of the sternocleidomastoid;
• horizontal plane formed by the lower margin of the mandible.

The anterior triangle of the neck can be further subdivided into (Clemente plate 436 fig. 693; Grant p. 752; Netter 3e 24, 4e 27-28):

• the submandibular (digastric) triangle between the posterior and anterior bellies of the digastric muscle and inferior border of the mandible.
• the carotid triangle between the posterior belly of the digastric, superior belly of the omohyoid and the sternocleidomastoid muscle.
• the muscular triangle between the superior belly of the omohyoid, lower anterior margin of the sternocleidomastoid and the median line of the neck.
• the submental triangle between the anterior bellies of the digastric and above the hyoid bone.

Landmarks:

1) The tips of the transverse processes of C1 are more prominent than those of other cervical vertebrae (Clemente plate 437 fig. 694; Grant p. 751; Netter 3e 26, 4e 19). Palpate in the parotid space (Clemente plate 435 fig. 691; Grant p. 750, Netter 3e 26, 4e 13).

2) The hyoid bone: Its body is at the level of C3. It has a lesser and greater horns (cornua) bilaterally.

3) The thyroid cartilage lies at the levels of C4 and C5.

• The laryngeal prominence is Adam's apple.
• The thyroid cartilage is composed 2 lateral laminae with superior and inferior horns (cornua; Clemente plate 558; Grant p. 751; Netter 3e 73, 4e 77).
• The inferior cornua articulate with the cricoid cartilage.

4) The cricoid cartilage lies at the level of C6 (Clemente plate 435; Grant p. 750; Netter 3e 12, 4e 65). The upper end of the trachea is palpable in the midline from the cricoid cartilage to the superior border of the manubrium.

5) The thyrohyoid membrane is pierced by the internal branches of the superior laryngeal nerve and vessels (Clemente plate 557; Grant p. 788-789; Netter 3e 76, 4e 71).

6) The cricothyroid membrane may be used for a high tracheostomy (Clemente plate 558; Grant p. 798; Netter 3e 73, 4e 77).

*The preferred site of tracheostomy is at tracheal cartilages 2-4 (below the cricoid cartilage and the isthmus of the thyroid gland).

SUPERFICIAL STRUCTURES

1) The platysma muscle (Clemente plate 438; Grant p. 746; Netter 3e 22, 4e 26)

2) The superficial (investing) layer of the deep cervical fascia (Clemente plate 446; Grant p. 747; Netter 3e 24, 4e 35):

• encloses the trapezius
• forms the roof of the posterior triangle
• invests the sternocleidomastoid muscle
• attaches to the mandible superiorly, and to the clavicle and manubrium inferiorly.

The single investing layer anteriorly covers the anterior triangle of the neck and fuses with the opposite fascia in the midline.

3) The superficial veins lie superficial to the deep fascia

Anterior jugular veins (Clemente plate 450; Grant p. 748; Netter 3e 27, 4e 31):

• lie in the midline:
• running from the submental triangle, they pierce the deep fascia above the manubrium.
• they pass between the posterior border of the sternocleidomastoid muscle and the upper border of the clavicle to drain into the external jugular veins in the posterior triangle of the neck.

4) Superficial cervical nerves (Clemente plate 441; Grant p. 754; Netter 20)

Sensory nerves from the cervical plexus:

• The great auricular nerve and transverse cervical nerves (anterior cutaneous nerve of neck) for C2 and C3 dermatomes.

The cervical branch of cranial nerve VII enters the platysma muscle on its deep surface near the angle of the mandible. This is a motor nerve.

INFRAHYOID MUSCLES (Grant p. 758-759, 761; Netter 3e 25, 4e 29)

• are depressors of the larynx and the hyoid bone.
• These strap muscles lie between the deep fascia and the visceral fascia covering the thyroid gland, trachea and esophagus.
• They are innervated by the ansa cervicalis (a motor plexus from the ventral rami of C 1, 2, and 3; Clemente plates 443, 444; Grant p. 762-763; Netter 3e 27, 28, 4e 32).

The ansa cervicalis

• C1 is carried by XII and forms the superior root.
• C2 and 3 are from the cervical plexus and form the inferior root.
• The ansa cervicalis joins superior and inferior roots and gives off major branches to the strap muscles.
• The ansa cervicalis lies lateral to the internal jugular vein and the carotid sheath.

Infrahyoid muscles (Clemente plate 447; Grant p. 758-759, 761; Netter 3e 25, 4e 29)

• Sternohyoid
• Omohyoid
• Thyrohyoid (C1 by XII)
• Sternothyroid is deepest

THE PHARYNX (Clemente plate 548; Grant p. 808-809; Netter 3e 64, 4e 63)

• is a derivative of the embryonic foregut
• is suspended from base of skull to C6
• lies between the bodies of the vertebrae and the larynx between C4-6.
• becomes continuous with the esophagus at C6.

The pharynx is formed by the superior, middle and inferior constrictors which are attached by a posterior midline raphé with the same constrictors on the opposite side (Clemente plate 550; Grant p. 786, 787; Netter 3e 71, 4e 67 & 68). From superior to inferior, the constrictor muscles are stacked into one another.

THE SUPERIOR CONSTRICTOR MUSCLE

• The superior constrictor muscle is not a constrictor (always open) and lies behind the nasal and oral cavities, continuous with the plane of the buccinator. Both of these muscles arise from the pterygomandibular raphé (Clemente plate 538, 548; Grant p. 788-789; Netter 3e 64, 4e 68).
• The superior constrictor also arises from the mylohyoid line of the mandible and the medial pterygoid plate.
• At the base of the skull, it attaches to the apex of the petrous temporal bone and the pharyngeal tubercle of the occipital bone (Clemente plates 498, 550; Grant p. 617; Netter 3e 63, 4e 67).

THE MIDDLE CONSTRICTOR MUSCLE lies behind the tongue and larynx (Clemente plates 550, 553; Grant p. 788, 791; Netter 3e 63, 4e 67). It is truly a constrictor and plays a major role in swallowing.

THE INFERIOR CONSTRICTOR MUSCLE attaches anteriorly to the cricoid and thyroid cartilages. The most inferior aspect is the cricopharyngeus which is the sphincter between the pharynx and the esophagus (Clemente plate 548; Grant p. 786, 788; Netter 3e 63-64, 4e 67-68).

Innervation (Clemente plate 551; Grant p. 787; Netter 3e 67, 72, 4e 71):

• The superior and middle constrictor muscles are innervated by the pharyngeal branches of the vagus nerve (cranial nerve X).
• The inferior constrictor muscle and the cricopharyngeus are innervated by recurrent branches of the vagus nerve.
• The swallowing reflex is performed by motor fibers and parasympathetic fibers of the vagus nerve.

The carotid sheath

• The carotid sheath contains the common carotid artery, internal jugular vein and the vagus nerve (Clemente plate 443, 446; Grant p. 747; Netter 28-29, 31, 4e 35).
• The artery is deep and medial to the internal jugular vein and the vagus is posterior to the carotid artery.
• The carotid sheath is anterior to the cervical sympathetic trunk which lies on the longus colli and longus capitis muscles in front of the cervical vertebrae (Clemente plate 452; Grant p. 774-775; Netter 3e 29, 31, 4e 71).

The thyroid gland

• is formed by 2 lobes lying lateral to the larynx and the trachea (Clemente plate 453; Grant p. 768-771; Netter 3e 65-66, 70-72, 4e 74-75). The lobes are connected by the isthmus at the level of tracheal cartilages 2-4.
• is overlapped by the sternothyroid muscles and related laterally to the carotid sheath.
• may have a pyramidal lobe (developmental origin in the tongue area; Clemente plate 454; Grant p. 769; Netter 3e 70, 4e 74).
• is vascularized by the superior (Clemente plate 454; Grant p. 770; Netter 3e 65, 4e 74) and inferior thyroid (Clemente plate 454; Grant p. 770, 772; Netter 3e 71-72, 4e 75) arteries.
• The recurrent laryngeal branches of the vagus nerves lie deep to the thyroid lobes near the posterior aspect of the trachea. These nerves are thus vulnerable in thyroid surgery.
• 4 parathyroid glands are associated with the posterior surface of the thyroid gland (Clemente plate 453; Grant p. 770; Netter 3e 71-72, 4e 76).

The carotid triangle

The posterior belly of the digastric (Clemente plate 439; Grant p. 761; Netter 3e 49, 4e 28, 32):

• comes from the medial surface of the mastoid process,
• attaches to the anterior belly of digastric by the intermediate tendon which is tied down by a fascial sling to the body of the hyoid.
• arises from the 2nd branchial arch and is innervated by cranial nerve VII, while the anterior belly (Clemente plate 447; Grant p. 760; Netter 3e 25, 28, 4e 28-29, 32) is derived from the 1st arch and receives its nerve supply from V3 (the mandibular division of the trigeminal nerve).
• is associated with the stylohyoid muscle which is also innervated by cranial nerveVII.

Relationships of the posterior belly of the digastric muscle:

1) between the posterior belly of the digastric muscle and the skin of the neck:

• The external jugular vein (Clemente plate 441; Grant p. 754; Netter  3e 27, 4e 31)
• The cutaneous branches of great auricular nerve
• The cervical branch of VII (Clemente plate 442; Grant p. 754; Netter 3e 21, 4e 25)

2) deep to the posterior belly of digastric

• The internal jugular vein (Clemente plate 443; Grant p. 763; Netter 3e 24-25, 28, 4e 31)
• The internal and external carotid arteries
• Cranial nerves X, XI, XII
• Deeper, cranial nerve IX (Clemente plates 444, 445, 551; Grant p. 789; Netter 3e 30, 4e 71) and the sympathetic trunk
  • The cranial nerve IX or glossopharyngeal nerve runs deep to the internal carotid artery and penetrates the lateral pharyngeal wall with the stylopharyngeus muscle (Clemente plate 551; Grant p. 789; Netter 3e 63, 119, 4e 68, 125). It is motor to this muscle and sensory to the mucosa of posterior 1/3 of tongue, mucosa of pharynx, palatine tonsil and soft palate.

Cranial nerve X or the vagus nerve lies in the carotid sheath and sends out (Grant p. 837; Netter 3e 28, 72, 4e 69):

• (upper branches) voluntary motor nerves to the muscles of palate (except for the tensor palati muscle which is innervated by V3), to the pharynx (except for the stylopharyngeus muscle ) and to the larynx.
• (lower branches) parasympathetic preganglionic fibers to the cervical, thoracic and abdominal regions
• sensory fibers with the inferior sensory ganglion lying in jugular fossa.
• sensory fibers to the skin of the external auditory canal with cell bodies lying in the superior sensory ganglion in the jugular fossa.

The superior laryngeal nerve from X divides into:

• The internal laryngeal branch which pierces the thyrohyoid membrane, is sensory to laryngeal mucosa above vocal cords and is involved in the coughing reflex.
• The external laryngeal branch which runs on the lateral aspect of the larynx to innervate the cricothyroid muscle which tenses vocal cords during vocalization.

Spinal portion of XI or accessory nerve (Clemente plate 551; Grant p. 838; Netter 3e 28, 121, 4e 32): test by flexing head, turning head and shrugging shoulders

XII or hypoglossal nerve (Clemente plate 445; Grant p. 835; Netter 3e 67, 122, 4e 71, 128), running deep to the middle tendon of digastric to get to the digastric triangle (Clemente plates 460-461; Grant p. 789, fig. 8.16; Netter 3e 27, 4e 71), is motor to the tongue musculature.

C1 anterior rami fibers ("hitchhikers") form the superior root of the ansa cervicalis and send a branch to the thyrohyoid muscle (Clemente plates 443, 444; Grant p. 780; Netter 3e 28, 4e 32).

Arteries

The common carotid artery divides at the level of C3 (hyoid bone).

• The internal carotid has the carotid sinus (baroreceptors associated with IX) at its beginning and no branches in the neck (Clemente plate 454, 458; Grant p. 765; Netter 3e 130, 4e 136).
• The carotid body is present at the bifurcation and has chemoreceptors.
• The carotid sinus and body are for mechanisms controlling blood pressure.

External carotid branches lie inferior to, deep to or superior to the posterior belly of the digastric.

Inferior to the posterior belly of the digastric:

1) The superior thyroid artery (Clemente plate 454, 474; Grant p. 770; Netter 3e 130, 4e 69) runs to the superior pole of the thyroid gland, anastomoses with its opposite counterpart and the inferior thyroid artery. Its branches are:

• The superior laryngeal artery running with the internal laryngeal nerve to become internal laryngeal artery and nerve (Clemente plate 454; Grant p. 770; Netter 3e 130, 4e 69).
• The cricothyroid branch running with the external laryngeal nerve.
• The muscular branch to the sternocleidomastoid muscle (Clemente plate 450; Grant p. 768).

2) The lingual artery supplies the tongue (Clemente plate 535 fig. 855; Grant p. 781-782; Netter 3e 55, 130, 4e 59, 69)

3) The ascending pharyngeal artery (at the bifurcation of the common carotid artery) supplies the lateral wall of the pharynx and the nasopharynx (Clemente plate 474; Grant p. 764; Netter  3e 130, 4e 69).

Deep to the posterior belly of the digastric:

• The facial artery (Clemente plate 474; Grant p. 764; Netter 3e 130, 4e 69)
• The occipital artery (lying superior to cranial nerve XII)

Superior to the posterior belly of the digastric:

• The posterior auricular branch (Clemente plate 474; Grant p. 662, 764; Netter 3e 130, 4e 69) with its stylomastoid branch (Clemente plate 712; Grant p. 704) supplying cranial nerve VII. Neuritis compresses the artery and leads to Bell's palsy.
• The maxillary artery (Clemente plate 478; Grant p. 668; Netter 3e 130, 4e 69)
• The superficial temporal artery (Clemente plate 476; Grant p. 662; Netter 3e 19, 4e 69)

The digastric triangle:

• contains the superficial lobe of the submandibular (submaxillary) salivary gland (Clemente plates 460, 461; Grant p. 762; Netter 3e 23-24, 4e 61).
• Its floor is formed by the mylohyoid, hyoglossus and middle constrictor muscles.

The Mylohyoid muscle (Clemente plate 534; Grant p. 760; Netter 23-24, 49)

• forms the floor of mouth (Clemente plate 535; Grant p. 761; Netter 3e 49, 4e 53). It is attached from the mylohyoid line to the superior aspect of body of hyoid bone and the midline raphé.
• The anterior belly of digastric lies superficially and both are derived from 1st branchial arch.
• They both are innervated by V3.

The Hyoglossus muscle runs from the greater cornu of the hyoid bone and inserts into the tongue (Clemente plate 538; Grant p. 782; Netter 3e 55, 4e 59). Cranial nerve XII lies against its external surface and the lingual artery lies against its internal surface (Clemente plate 535 fig. 855; Grant p. 780; Netter 3e 55, 65, 67, 4e 59).

updated 10/28/2009

THE ROOT OF THE NECK

Scalene anterior muscle (Clemente plate 456; Grant p. 774-776; Netter 3e 26, 4e 30) :

• from the anterior tubercles of C3-6 vertebrae
• to the scalene tubercle on the superior surface of rib 1
• is the key orienting structure in this region.

Sternoclavicular joint (Grant p. 26; Netter 3e 208, 4e 30, 33)

• On the right, the brachiocephalic trunk divides into subclavian and common carotid arteries posterior to the sternoclavicular joint.
• On the left, the left common carotid and left subclavian arteries ascend posterior to the sternoclavicular joint.

The subclavian artery runs over the apex of the lung, posterior to the scalene anterior and superior to rib 1.

The subclavian artery can be divided into 3 parts:

• Medial to scalenus anterior;
• Posterior to scalenus anterior;
• Lateral to scalenus anterior (in the posterior triangle of the neck above rib 1).

The subclavian vein (Clemente plate 452; Grant p. 488, 772-773; Netter 3e 29, 194, 208, 4e 30) has 3 important differences from the artery:

• It lies inferior to the artery, within the arch formed by the artery over the apex of the lung.
• It passes anterior to scalenus anterior at the insertion point on rib 1.
• It is posterior and inferior to the clavicle (intravenous catheterization must be done from the inferior aspect of clavicle).

Triangle of the vertebral artery:

• Scalenus anterior muscle (Clemente plate 456; Grant p. 774-776; Netter 3e 29, 4e 30)
• Longus colli muscle
• The superior aspect of the subclavian artery

Contents of the triangle of the vertebral artery:

• The vertebral artery (Clemente plates 458, 459; Grant p. 776; Netter 3e 29, 4e 33) and vein ascend to the apex of triangle and enter the foramen transversarium of C6.
• The sympathetic trunk (on the anterior aspect of longus colli) with associated middle (at the level of the inferior thyroid artery) and inferior cervical ganglia (on the posterior aspect of the origin of the vertebral artery).
• The common carotid artery runs on the anterior aspect of the triangle to lie anterior to the origins of scalenus anterior. It can be compressed on the transverse process of C6 (the carotid tubercle).
• The carotid sheath contains the common carotid artery, internal jugular vein and vagus nerve (Clemente plate 452; Grant p. 786; Netter 3e 28, 4e 35). It is located on the medial border of the scalenus anterior.
• The right recurrent laryngeal nerve arises from the vagus and loops under the right subclavian artery (Clemente plate 554; Grant p. 772; Netter 3e 29, 31, 4e 33) to ascend to the larynx between the trachea and the esophagus.
  • The most inferior aortic arch retained in embryonic development on the right is the 4th aortic arch and it forms the initial segment of the right subclavian artery. On the left side, the 6th aortic arch is retained as the ductus arteriosus and the left recurrent laryngeal nerve loops around it.
• The phrenic nerve (Clemente plate 452; Grant p. 773; Netter 3e 29, 4e 33) lies in the inferolateral corner of the triangle on the anterior surface of the subclavian artery. It crosses the anterior surface of the subclavian artery and the apex of the lung to enter the thorax.
• The left phrenic nerve is crossed by the thoracic duct which joins the bifurcation of the left brachiocephalic vein.
• The right lymphatic duct joins the bifurcation of the right brachiocephalic vein (Clemente plate 455; Grant p. 43; Netter 3e 204, 228, 4e 208).

Branches of the 1st part of the subclavian artery

1) The vertebral artery is the largest branch and lies in the transverse foramina of C1-C6 (Clemente plate 458; Grant p. 764-765; Netter 3e 130, 4e 136).

2) The thyrocervical trunk

• The inferior thyroid artery (Clemente plate 459; Grant p. 770-771; Netter 3e 29, 4e 33, 136) forms a loop at C6 associated with the middle cervical ganglion and supplies the inferior pole of the thyroid gland (Clemente plate 454; Grant p. 771-772; Netter 3e 29, 71-72, 4e 76). It anastomoses with the superior thyroid artery coming from the external carotid artery. It supplies the scalenus anterior and the longus colli muscles by its ascending cervical artery.
• The transverse cervical artery and suprascapular artery pass anterior to scalenus anterior and clamp down the phrenic nerve as they run into the posterior triangle of the neck.

3) The internal thoracic artery (Clemente plate 459 fig. 721; Grant p. 773; Netter 3e 29, 4e 33) runs in the pleura, posterior to the subclavian vein and enters the thorax on the posterior aspect of the sternum.

4) The costocervical trunk (Clemente plate 459; Grant p. 75, 764; Netter 3e 29, 4e 33, 136-138)

• passes posteriorly over the apex of the lung and the neck of rib1.
• gives out the deep cervical artery for the deep musculature for the back of the neck.
• continues as the superior (highest) intercostal artery which gives out the 1st posterior intercostal artery and a branch to the 2nd posterior intercostal artery

Phrenic nerve:

• from the anterior rami of C3-5
• is formed at the superior lateral portion of the scalenus anterior and courses to the medial border of this muscle (Clemente plate 452; Grant p. 774; Netter 3e 29, 4e 32).
• is in the prevertebral fascia and is crossed anteriorly by the suprascapular and transverse cervical arteries (Clemente plate 444; Grant p. 757; Netter 3e 28-29, 4e 32-33).
• is motor to the diaphragm, sensory to the parietal pleura and the peritoneum covering the diaphragm.

The trachea and esophagus (cervical portions)

• from C6 to the superior aperture of the thorax (T1, rib1 and manubrium; Clemente plate 99 fig. 160, plate 549; Grant p. 750; Netter 3e 67, 4e 65 & 68).
• They are invested in the visceral (pretracheal) fascia along with the thyroid gland (Clemente plate 446; Grant p. 768-769; Netter 3e 31, 4e 35).
• This visceral column lies between the 2 carotid sheaths and anterior to the bodies of the vertebrae and the prevertebral fascia in the root of the neck.

updated 10/28/2009

THE PHARYNX AND THE PALATE

The pharynx:

• is related to the prevertebral fascia posteriorly (Clemente plate 457; Grant p. 747; Netter 3e 31, 4e 35) and the carotid sheath posterolaterally (Clemente plate 457; Grant p. 747, 786-787; Netter 3e 65, 4e 70).
• is attached superiorly to the basiocciput at the pharyngeal tubercle (Clemente plate 550; Grant p. 787; Netter 8), medial tip of the petrous bone and the medial pterygoid plate of the sphenoid bone.
• extends inferiorly to C6, being continuous with the esophagus (this first esophageal constriction is a site for obstruction; Clemente plate 548; Grant p. 786-787, 808-809; Netter 3e 63, 4e 66).

PHARYNGEAL WALL

4 layers (from exterior to interior)

1. Visceral fascia: also covers the external surface of the buccinator muscle (buccopharyngeal fascia) and the superior constrictor muscle. The common origin of these 2 muscles is the pterygomandibular raphé (Clemente plate 548; Grant p. 788-789; Netter 3e 64, 4e 65).

The pharyngeal plexus of veins:

• lies deep to this fascia, draining the pharynx, soft palate and the pharyngeal tonsil.
• communicates with the pterygoid plexus of veins (Clemente plate 551; Grant p. 639; Netter 3e 66, 4e 70) and drains into the internal jugular vein.
• These veins have no valves and infection from the pharynx, palate and tonsils may spread (septicemia) systemically or into the meningeal venous plexus.

The pharyngeal nervous plexus is formed by (Clemente plate 551; Grant p. 788-789; Netter 3e 67, 4e 71):

• the skeletal and parasympathetic motor branches of X,
• sensory branches of IX,
• and vasomotor branches of the sympathetic system.

2. Skeletal muscular wall: 5 paired skeletal muscles.

3 muscles form the circular layer: the superior, middle and inferior constrictor muscles (Clemente plate 550; Grant p. 788; Netter 3e 64, 4e 67).

• The interval between the superior constrictor and base of the skull: allows for:
  • transmission of the auditory tube from the base of the skull to the nasopharynx (Clemente plates 471, 553; Grant p. 712, Netter 4e 67),
  • and transmission of the ascending pharyngeal artery (Clemente plate 551; Grant p. 786; Netter 3e 65, 4e 69).
• The interval between superior and middle constrictor allows for transmission of the stylopharyngeus and cranial nerve IX (Clemente plates 550, 551; Grant p. 788-789; Netter 3e 61, 63, 4e 68-69, 71).
• The interval below the origin of the middle constrictor is covered by the thyrohyoid membrane and transmits the internal laryngeal nerve and artery into the larynx.
• Below the inferior constrictor, the inferior laryngeal artery (from the inferior thyroid artery) and the recurrent laryngeal nerve pierce the pharyngeal wall to enter the larynx.

2 muscles are longitudinal and run from base of skull and palate vertically to attach to the thyroid cartilage: the stylopharyngeus and palatopharyngeus. Both insert into the thyroid cartilage on the internal aspect of the middle and inferior constrictors. They are separated superiorly by the superior constrictor muscle.

Stylopharyngeus (Clemente plate 550; Grant p. 787, 789; Netter 3e 64, 4e 68):

• arises from the styloid process external to the superior constrictor at the base of the skull.
• descends and enters the pharyngeal cavity with IX (is innervated by this cranial nerve) between the superior and middle constrictor muscles.
• elevates the larynx during swallowing.

Palatopharyngeus (Clemente plate 553; Grant p. 795; Netter 3e 63, 4e 65, 67):

• attaches from the palate and lateral wall of the nasopharynx, on the internal aspect of the superior constrictor muscle.
• The overlying mucosa forms the palatopharyngeal arch, posterior to the palatine tonsil.
• is innervated by X.
• A superior extension of the palatopharyngeus onto the lateral nasal wall and the cartilage of the auditory tube is called the salpingopharyngeus muscle (with the overlying salpingopharyngeal fold; Clemente plates 552, 554; Grant p. 795; Netter 3e 60, 61, 4e 64-67).

3. The fibrous internal muscular fascia

4. The mucosal lining

INTERIOR OF THE PHARYNX AND THE PALATE:

The interior of the pharynx is divided into naso-, oro-, and laryngopharynx (Clemente plate 549; Grant p. 790; Netter 3e 59, 4e 66).

The soft palate separates the nasopharynx from the oropharynx and acts as a flap-valve between these 2 regions to allow continuity between these 2 regions during respiration.

The nasopharynx:

• The choanae are the right and left posterior nasal apertures.
• The lateral and posterior walls are formed by the mucosa lining (Clemente plate 552; Grant p. 790, 794; Netter 3e 59, 4e 66) the inside of the upper part of the superior constrictor muscle and the 2 palatal muscles surrounding the opening of the auditory tube (levator palati and tensor palati; Clemente plate 553; Grant p. 791, 795; Netter 3e 60, 65). Even when muscles contract, the nasopharynx remains open to insure the patency of the respiratory airway.
• Posteriorly lie the opening of the Eustachian (auditory) tube surrounded by the salpingopharyngeal fold and the tubular tonsil (which may enlarge during an infection)..
• The nasopharyngeal tonsils are located on the posterior and superior walls of the pharynx. When they become enlarged, they are called adenoids and may turn the individual into a mouth-breather. Adenoidectomy is indicated.

The oropharynx lies inferior to the soft palate (Clemente plate 552; Grant p. 790; Netter 3e 59, 4e 63, 66) and superior to the root of the tongue.

• The oropharynx is continuous with the oral cavity anteriorly and it is demarcated by the palatoglossal arches (Clemente plate 538; Grant p. 794; Netter 3e 60, 4e 64). During development, this is the site of the embryonic buccopharyngeal membrane separating the ectodermal stomodeum from the endodermal foregut).
• The palatoglossus muscle (Clemente plate 539 fig. 860; Grant p. 792-795; Netter 3e 60, 4e 64), underlying the palatoglossal folds is a depressor of the soft palate and is innervated by X. It lies anterior to the palatine tonsil, attaching to the side of the tongue at the junction between its anterior 2/3 and posterior 1/3.
• The palatopharyngeus muscle lies posterior to the palatine tonsil. It elevates the larynx during swallowing and depresses the soft palate during respiration. It is innervated by X.
• The palatine tonsil is contained in the triangular area (the fauces) between the 2 muscles (pillars; Clemente plate 539; Grant p. 793-795; Netter 3e 60, 4e 64) .
  • The palatine tonsils are THE "tonsils" and are located in the oropharynx inferior to the soft palate.
  • The palatine tonsil is vascularized by the tonsillar branches of the ascending pharyngeal and facial arteries (Clemente plate 557; Grant p. 793-797; Netter 3e 60, 4e 64). The lingual artery may also provide tonsillar branches. The tonsils may bleed extensively during tonsillectomy.
  • The mucosa over the tonsils is innervated by sensory branches of IX; stimulation provokes the gag reflex (this is a test for the sensory component of IX).
• The soft palate is innervated by V2 and the lateral pharyngeal wall by X (which also provokes the gag reflex).
  • Test the parasympathetic component of nerve IX by observing the parotid secretion from the parotid papilla (opposite the 2nd upper molar tooth in the mouth).
  • Test the motor component of IX (innervating the stylopharyngeus) and X (innervating the palatopharyngeus) by observing the elevation of the larynx during swallowing.

Laryngopharynx lies posterior to the opening of the larynx at C3-4.

• The opening of the larynx is obliquely oriented. It is bounded anteriorly by the epiglottis, and posteriorly by the mucosa and muscles attaching to the arytenoid cartilages (Clemente plates 549, 553; Grant p. 790-791; Netter 3e 73, 4e 65, 77). The lateral walls of the pharynx here form the aryepiglottic folds (Clemente plate 553; Grant p. 790; Netter 62).
• During swallowing, elevation of the larynx, contraction of the aryepiglottic folds and posteroinferior tilting of the epiglottis closes the inlet to the larynx and direct food and drink into the lateral aryepiglottic folds.
• During breathing, the larynx descends and the tongue protrudes forward.

Between the anterior surface of the epiglottis and the posterior surface of the tongue are the valleculae separated by a glossoepiglottic fold (Clemente plate 539; Grant p. 790; Netter 3e 60, 4e 64). The vallecular fossae communicate with the piriform recesses lateral to the aryepiglottic folds. This is the territory of the internal branch of the superior laryngeal nerve (X), which is sensory for the cough reflex and also innervates the mucosa lining interior of larynx, superior to the vocal cords (also an area for eliciting the cough reflex; Clemente plate 554; Grant p. 800; Netter 3e 61, 4e 65).

The PALATE separates the oral from the nasal cavities.

The hard palate is formed anteriorly by the palatine processes of the maxilla and horizontal processes of the palatine bone (Clemente plate 498; Grant p. 682; Netter 8,10). It is covered over and under by mucoperiosteum. The rugae may be observed in the anterior 1/3 of the oral surface.

The soft palate lies posteriorly separating oropharynx from nasopharynx.

Innervation of the mucosa is by V2:

• The anterior 1/3 of the hard palate is innervated by the nasopalatine nerve which reaches the mouth via the incisive foramen (Clemente plate 524; Grant p. 683; Netter 3e 39, 4e 43).
• The posterior 2/3 of the hard palate is innervated by the greater palatine nerve branching from V2 in the pterygopalatine fossa (Clemente plate 526; Grant p. 683; Netter 3e 39, 48, 4e 43, 52) and entering the mouth via the greater palatine foramen.
• The mucosal membrane of the soft palate receives innervation via the lesser palatine nerves, entering into the mouth via the lesser palatine foramina.
• Postganglionic parasympathetic secretomotor fibers accompany these sensory branches of V2: preganglionic parasympathetic fibers via the greater (superficial) petrosal nerve (VII), synapse in the pterygopalatine ganglion (Clemente plate 527; Grant p. 831; Netter 3e 40, 4e 43-44).
• Taste fibers also from VII run with the greater (superficial) petrosal nerve. The cell bodies are in the geniculate ganglion.

The greater palatine artery (Clemente plate 526; Grant p. 683-684; Netter 3e 37, 4e 40-41, 52) supplies the oral mucosa of the entire hard palate and ascends through the incisive foramen to supply a portion of the nasal septum and anastomose with the sphenopalatine artery (Clemente plate 524 fig. 830; Grant p. 683; Netter 3e 37, 4e 40).

Muscles of the soft palate (Clemente plates 471, 553; Grant p. 684; Netter 3e 63, 64, 4e 64-65)

• The levator palati arises from the apex of the petrous bone and inserts into the palatal aponeurosis on the upper soft palate. It is innervated by pharyngeal branch of X (Test by saying "AH" and watching the elevation of the uvula in the midline. Deviation is away from the lesioned side).
• The tensor palati arises from the base of the skull, anterior to the cartilaginous auditory tube. It runs down, wraps itself around the hamulus of the medial pterygoid plate (Clemente plate 527 fig. 835; Grant p. 681, 683-684; Netter 3e 60, 4e 14) and inserts into the soft palatal aponeurosis. It tenses the soft palate and is innervated by V3.

Levator and tensor palati also open the auditory tube thus relieving pressure difference between the middle ear and the nose.

updated 10/28/2009

THE PREVERTEBRAL REGION

The deep anterior cervical muscles are grouped according to their relationships with the cervical and brachial plexuses (Clemente plate 456; Grant p. 774-776; Netter 3e 26, 4e 30, 32).

Muscles lying medial to the plexuses include the:

• Rectus Capitis Anterior, attached between C1 vertebra and the base of the skull.
• Longus colli (cervicis), attached from the body of T3 vertebra to the anterior tubercle of C1 vertebra and to the bodies of all vertebrae in-between. It is attached to the anterior tubercles of C3-6 vertebrae and the cervical sympathetic trunk lies on it to ascend in the neck.
• Longus Capitis, attached from the anterior tubercles of C3-6 vertebrae to the basiocciput, posterior to the pharyngeal tubercle. It is also related to the sympathetic trunk.
• Scalenus anterior, attached from the anterior tubercles of C3-C6 vertebrae to the scalene tubercle on upper aspect of rib 1. It is the key muscle in the root of the neck:
  • The brachial plexus and the second part of the subclavian artery are posterior to this muscle.
  • The subclavian vein, phrenic nerve, suprascapular artery and transverse cervical artery are anterior.
  • The carotid sheath (Clemente plate 452; Grant p. 772, 773; Netter 3e 27, 29, 4e 33), sympathetic chain, thyrocervical trunk and vertebral artery are medial.

Muscles lying lateral to the plexuses include the:

• Rectus Capitis Lateralis atttached between C1 vertebra and the base of skull. Cranial nerve XII (hypoglossal) and the anterior ramus of C1 spinal nerve emerge between the rectus capitis anterior and lateralis to course anteriorly to the neck.
• Scalenus Medius and Posterior, which together form the Scalene Mass (Clemente plates 449, 452; Grant p. 774; Netter 3e 26, 4e 32)
• Levator Scapulae

The scalene mass and the levator scapulae arise from the posterior tubercles of the cervical vertebrae and insert into ribs 1 and 2, and the superior angle of the scapula, respectively.

The prevertebral fascia (Clemente plate 446 fig. 705; Grant p. 774; Netter 3e 31, 4e 35) covers these prevertebral muscles, forming the fascia of the floor of the posterior triangle of the neck and is carried laterally by the brachial plexus and the subclavian artery to form the axillary fascia . This prevertebral fascia lies posterior to the retropharyngeal space and behind the danger plane.

updated 10/28/2009

The larynx is the organ for vocalization and lies between the levels of C4 and C6 vertebrae (Clemente plate 549; Grant p. 747; Netter 3e 59, 4e 63).

The cricoid cartilage

• is at the level of C6 vertebra.
• its anterior arch is attached superiorly to the thyroid cartilage by the cricothyroid membrane. The thickened midline portion of this membrane is the median cricothyroid ligament (Clemente plate 558 fig. 899; Grant p. 798; Netter 3e 73, 4e 77).
• Its posterior aspect is the posterior lamina (Grant p. 799; Clemente plate 558 fig. 900).

The thyroid cartilage

• Right and left laminae fuse anteriorly in the midline. The angle of fusion is more acute in the male and forms the laryngeal prominence (Adam's apple) after puberty (Clemente plate 558 fig. 899; Grant p. 798; Netter 3e 73, 4e 77).
• Each lamina has superior and inferior horns and an oblique line (Clemente plate 560 fig. 904; Grant p. 798; Netter 3e 73, 4e 77) for the attachment of the sternothyroid, thyrohyoid (Clemente plate 449; Grant p. 768; Netter 3e 25, 4e 29) and inferior constrictor (Clemente plate 449; Grant p. 788-789; Netter 3e 64, 4e 68) muscles.
• The upper border of the thyroid cartilage is attached to the hyoid bone by the thyrohyoid membrane (Clemente plate 560 fig. 904; Grant p. 798; Netter 3e 73, 4e 77) which is pierced by the internal (branch of the superior) laryngeal nerve (X) and the superior laryngeal artery (from the superior thyroid artery; Clemente plate 557; Grant p. 800, 802; Netter 3e 72, 4e 76).
• The inferior horns of the thyroid cartilage articulate with the cricoid cartilage.

The cricothyroid muscle (Clemente plate 560 fig. 904; Grant p. 768, 802; Netter 3e 74, 4e 78):

• from the upper border of the cricoid arch
• to the lower border of the thyroid lamina and inferior horn.
• its contraction tilts the thyroid cartilage, resulting in tension of the vocal cords (Clemente plate 560 fig. 904; Grant p. 802; Netter 3e 75, 4e 79).
• is innervated by the external laryngeal nerve from the superior laryngeal nerve (X).

The arytenoid cartilages

• sit on top of the cricoid lamina (Clemente plate 558 fig. 900; Grant p. 798-799; ; Netter 3e 73, 4e 77).
• control the opening between the vocal cords, the rima glottidis.
• attach to the vocal ligament by the anterior vocal process (Clemente plate 559 fig. 902; Grant p. 798-799; Netter 3e 73, 4e 77).
• The lateral muscular process serves as attachment points for muscles of the larynx.
• The apex of the arytenoid cartilages attach to the aryepiglottic folds, with a small extension formed by the corniculate cartilages.

A cuneiform cartilage can also be found in the aryepiglottic fold, anterior to the arytenoid cartilage.

The vocal ligaments

• attach between the vocal processes of the arytenoid cartilages and the thyroid cartilage, behind its fusion angle (Clemente plate 559 figs. 901, 902; Grant p. 799, 801; Netter 3e 74, 4e 78-79).
• are actually the superior border of the cricothyroid membrane (the conus elasticus; Clemente plate 559 figs. 902, 903; Grant p. 798-801; Netter 3e 74, 4e 78).

This is why damage to the cricothyroid ligament in a tracheostomy may affect the vocal ligaments and the voice.

The epiglottis:

• is leaf-shaped
• its stem is attached above the angle of fusion of the thyroid cartilage by the thyro-epiglottic ligament (Clemente plate 558 fig. 900; Grant 799; Netter 3e 73, 4e 77).

The quadrangular membrane

• attaches to the lateral borders of the epiglottis anteriorly and the arytenoid cartilages posteriorly (Clemente plate 561 fig. 907, plate 562; Grant p. 799; Netter 3e 59, 73; 75, 4e 63, 78).
• The free superior border of the quadrangular membrane is the aryepiglottic ligament and the free inferior border forms the vestibular ligament.

The intrinsic muscles of the larynx are all innervated by the recurrent laryngeal nerves (from cranial nerve X; Clemente plate 557; Grant p. 800, 802; Netter 3e 76, 4e 80) and are located on the posterior and lateral aspects of the larynx.

2 POSTERIOR MUSCLES:

The posterior cricoarytenoid muscle:

• from the posterior surface of the lamina of the cricoid cartilage
• to the posterior aspect of the muscular process of the arytenoid cartilage.
• This is THE abductor of the vocal cords and it opens the rima glottidis (Clemente plate 560 fig. 905, plate 561 fig. 906; Grant p. 799, 802, 804; ; Netter 3e 74-75, 4e 78-79) during respiration. (All other intrinsic muscles close the rima glottidis; (Clemente plate 560 fig. 905, plate 561 fig. 906; Grant p. 803; Netter 3e 75, 4e 79).
• Bilateral paralysis of the posterior cricoarytenoids due to damage of the recurrent laryngeal nerves is a respiratory emergency and may require a tracheostomy.

The arytenoideus muscle

• attaches to the posterior aspects of the 2 arytenoid cartilages (Clemente plate 560 fig. 905, plate 561 fig. 906; Grant p. 802; Netter 3e 74, 4e 78).
• Its contraction will adduct the arytenoid cartilages, vocal processes and vocal cords.
• Some fibers of this muscle form the aryepiglotticus in the aryepiglottic fold (Clemente plate 560 fig. 905, plate 561 fig. 906; Grant p. 803; Netter 3e 74, 4e 78).

5 LATERAL MUSCLES

attach to the anterior aspects of the arytenoid cartilages and adduct the vocal cords (Clemente plate 561 fig. 906; Grant p. 803; Netter 3e 74-75, 4e 78-79).

The lateral cricoarytenoid muscle attaches from the superior aspect of the arch of the cricoid to the anterior surface of the muscular process of the arytenoid cartilage.

The thyroarytenoideus muscle from the internal surface of the angle of the thyroid cartilage to the lateral aspect of the arytenoid cartilage. The portion adjacent to the vocal ligament is the vocalis muscle (Clemente plate 561 fig. 907; Grant p. 801; ; Netter 3e 74-75, 4e 78-79).

The thyroepiglotticus lies on the medial surface of the quadrangular ligament. It is formed by upper fibers of thyroarytenoideus, which join with aryepiglotticus to run to the epiglottis.

The aryepiglotticus lies on the superior border of the quadrangular ligament in the aryepiglottic fold .

• In RESPIRATION, the horizontal fibers of the posterior cricoarytenoid muscles abduct the vocal processes and open the rima glottidis. The vertical fibers of the posterior cricoarytenoid muscles pull the arytenoid cartilages laterally to further open the rima glottidis.
• In VOCALIZATION, the vocal cords are adducted to produce vocal sounds.

Paralysis of one of the posterior cricoarytenoids causes a whisper to the quality of the voice. Tension is affected by the vocalis and cricothyroid muscles.

• SPHINCTER FUNCTION: Adduction of the vocal cords is performed in increasing intraabdominal pressure. It also occurs in the "coughing" reflex to increase the force of expiration and remove the stimuli.
• In SWALLOWING:

The aryepiglottic, thyroarytenoid and thyroepiglottic muscles:

• close the vestibule,
• tilt the arytenoid cartilages anteriorly
• and assist in depressing the epiglottis as the larynx is elevated during swallowing.

This closes the superior laryngeal aperture and divert the swallowed food to the piriform recesses.

The INTERIOR OF THE LARYNX

The superior laryngeal aperture is obliquely oriented and bounded by the aryepiglottic folds and mucosa on the posterior aspect of the epiglottis.

The supraglottic cavity (Clemente plate 562; Grant p. 801, 804; Netter 3e 59, 4e 63) above the vocal folds has the vestibule (between the aryepiglottic folds and the vestibular folds - false vocal cords) and the ventricles (between the true and false vocal cords). Sensory innervation is by the internal (branch of the superior) laryngeal nerve, which pierced the thyrohoid membrane (Clemente plate 557; Grant p. 802; ; Netter 3e 76, 4e 76, 80).

The transition from stratified squamous epithelium superiorly to ciliated pseudostratified columnar epithelium inferiorly occurs at the level of the vocal cords and is a common site for cancer.

The infraglottic cavity is inferior to the vocal cords and continuous with the trachea. Its sensory innervation is by the recurrent laryngeal nerves (mixed-motor to all laryngeal muscles except for the cricothyroid muscle) which pierced the cricothyroid membrane.

The blood supply is by the laryngeal branches of the superior and inferior thyroid arteries (Clemente plate 557; Grant p. 770-771; Netter 3e 72, 4e 76) accompanying the internal (Clemente plate 557; Grant p. 802; Netter 3e 72, 4e 76) and recurrent (Clemente plate 557; Grant p. 802; Netter 3e 76, 4e 80) laryngeal nerves, respectively.

updated 10/28/2009

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