Dissector Answers - Larynx and Neck

Learning Objectives:

Upon completion of this session, the student will be able to:

  1. Identify and list the attachments, innervation and action of the muscles of the neck: sternocleidomastoid, infrahyoid muscles, scalene muscles.
  2. Identify the boundaries of the anterior and posterior cervical triangles and their subdivisions.
  3. Describe the branches of the cervical plexus.
  4. Identify the deep cervical fascia, its various component layers, and the resulting compartmentalization of the neck.
  5. Locate and describe the specific features of the thyroid gland.
  6. Give the position of the parathyroid glands and consider the thyroid/parathyroid gland relationship in terms of vascular supply and surgical intervention.
  7. Identify and list the parts and branches of the subclavian artery and vein, and describe their course in the neck.
  8. In the root of the neck, locate the vagus and phrenic nerves and describe their relationships to the organs, fascia, vessels, and viscera of the neck.
  9. Describe the anatomy relevant to subclavian vein catheterization: surface landmarks and relationships of the subclavian vein to the clavicle, 1st rib, subclavian artery, brachial plexus, parietal pleura, phrenic and vagus nerves.
  10. Identify the deep cervical lymph nodes and explain their significance.
  11. Review the arrangement, distribution and function of the cervical sympathetic trunk.
  12. Review the carotid sheath and contents.
  13. List the basic functions of the larynx.
  14. Identify the main cartilages and membranes that form the internal framework (skeleton) of the larynx.
  15. Describe the actions of the intrinsic muscles of the larynx in tensing, relaxing, abducting or adducting the vocal folds.
  16. Describe the innervation and vascular supply of the larynx.
  17. Describe the anatomy relevant to cricothyroidotomy: locate the cricothyroid membrane and describe its relationships to the thyroid and cricoid cartilages, vocal cords, cricothyroid artery, and cricothyroid muscles.

Learning Objectives and Explanations:

1. Identify and list the attachments, innervation and action of the muscles of the neck: sternocleidomastoid, infrahyoid muscles, scalene muscles. (N27,N28,N29,N31, N30, N32, N33, N186, N192, N194, N429, TG7-12, TG7-13, TG7-15A, TG7-15B, TG7-16, TG7-17, TG7-18)

The names of these muscles are helpful in identifying their locations. For example: "omo" means shoulder, and omohyoid goes from the shoulder to the hyoid bone.

Muscles

MuscleOriginInsertionActionInnervationNotesImage
omohyoid (TG7-10, TG7-12) inferior belly: upper border of scapula medial to scapular notch; superior belly: intermediate tendoninferior belly: intermediate tendon; superior belly: lower border of hyoid lateral to sternohyoid insertiondepresses/stabilizes hyoid boneansa cervicalisthe intermediate tendon of omohyoid is tethered to the clavicle by a fascial sling
sternohyoid (TG7-12, TG7-13) posterior surfaces of manubrium and sternal end of claviclelower border of hyoid bone, medial to omohyoid insertiondepresses/stabilizes hyoid boneansa cervicalissternohyoid overlies sternothyroid and thyrohyoid
sternothyroid (TG7-12, TG7-13)posterior surface of manubrium below sternohyoid originoblique line of thyroid cartilagedepresses/stabilizes thyroid cartilage of larynxansa cervicalissternothyroid lies deep to sternohyoid
thyrohyoid (TG7-12, TG7-13)oblique line of thyroid cartilagelower border of hyoid boneelevates larynx; depresses/stabilizes hyoid boneC1&2 fibers running with hypoglossal nerve that leave XII anterior to the superior root of ansa cervicalisthyrohyoid lies deep to the sternohyoid
sternocleidomastoid (TG7-12, TG7-13)sternal head: anterior surface of manubrium; clavicular head: medial 1/3rd of claviclemastoid process and lateral 1/2 of superior nuchal linedraws mastoid process down to same side; turns chin up toward opposite sidespinal accessory nerve (XI), with sensory supply from C2 & C3 (for proprioception)carotid sheath structures lie deep to it
scalene, anterior (N28, N30, N32, TG7-15A, TG7-15B, TG7-17, TG7-18) anterior tubercles of transverse processes of vertebrae C3-C6scalene tubercle of first ribelevates first rib; flexes and laterally bends the neckbrachial plexus, C5-C7a muscle of inspiration; anterior scalene inserts behind the subclavian vein, and anterior to the subclavian artery and roots of the brachial plexus (Greek, skalenos = uneven, having sides of unequal length)
scalene, middle (N28, N30, N32, TG7-15A, TG7-15B, TG7-17, TG7-18)posterior tubercles of the transverse processes of vertebrae C2-C7upper surface of first rib behind subclavian arteryelevates first rib; flexes and laterally bends the neckbrachial plexus, C3-C8a muscle of respiration (inspiratory); also called scalenus medius; penetrated by the dorsal scapular n. and long thoracic n. (Greek, skalenos = uneven, having sides of unequal length)
scalene, posterior (N28, N30, N32, TG7-15A, TG7-15B, TG7-17, TG7-18)posterior tubercles of the transverse processes of vertebrae C5-C7lateral surface of second ribelevates second rib; flexes and laterally bends the neckbrachial plexus, C7-C8a muscle of respiration (inspiratory) (Greek, skalenos = uneven, having sides of unequal length)
Nerves and their relations to the scalene muscles and 1st rib: Arteries and veins and their relations to the scalenes and 1st rib:
2. Identify the boundaries of the anterior and posterior cervical triangles and their subdivisions. (N 28, TG 7-02A, 7-02B)
3. Describe the branches of the cervical plexus. (W & B 191 and Fig 190; N 24,31,32,129,178, TG 7-11, 7-16A,7-16B, 7-13)
The cutaneous branches of the cervical plexus include the lesser occipital, the great auricular, the transverse cervical, and the supraclavicular nerves. They emerge along the lateral border of the sternocleidomastoid muscle in the order of lesser occipital, great auricular, transverse cervical, and supraclavicular (superior to inferior). (Note: Netter 31 incorrectly indicates that the great auricular is superior to the lesser occipital. The lesser occipital comes from C2 and the great auricular comes from branches of C2 and C3.)

Nerve Source Location Area of distribution
Lesser occipital C2 Ascends in the neck along the posterior border of the sternocleidomastoid muscle; pierces the cervical fascia near the muscle and divides into branches Skin and subcutaneous tissue behind the ear
Great auricular C2, C3 Appears at the lateral border of the sternocleidomastoid muscle just below the lesser occipital nerve and goes toward the auricle and the angle of the mandible Skin of the ear and below the ear
Transverse cervical C2, C3 Appears below the great auricular nerve at the lateral border of the sternocleidomastoid muscle; crosses the muscle horizontally to reach the anterior triangle deep to the platysma muscle and the external jugular vein Skin of the neck anteriorly
Supraclavicular C3, C4 Emerges below the transverse cervical nerve at the lateral edge of the sternocleidomastoid muscle; descends through the inferior part of the posterior triangle and divides into three branches that pierce the platysma near the clavicle Skin of the root of the neck; upper chest and upper shoulder anteriorly

Cervical Plexus

Nerve Source Branches Motor Sensory Notes
cervical plexus ventral primary rami of spinal nerves C1-C4 brs. to: longus colli & capitis, sternocleidomastoid m., trapezius m., levator scapulae m., scalenus medius m., rectus capitis anterior and lateralis mm.; superior & inferior root of the ansa cervicalis, n. to the thyrohyoid m., n. to the geniohyoid m., lesser occipital n., great auricular n., transverse cervical n., supraclavicular nn. (medial, intermediate and lateral), contributions to the phrenic n. from C3 and C4 longus colli & capitis mm., rectus capitis anterior & lateralis mm., infrahyoid mm., thyrohyoid m., geniohyoid m., respiratory diaphragm skin of the anterolateral neck; skin of the ear and skin behind the ear close association of the supraclavicular nn. to the phrenic n. results in pain from the respiratory diaphragm referred to the shoulder

4. Identify the deep cervical fascia, its various component layers, and the resulting compartmentalization of the neck. (W & B 191-195 and Fig 3-6, N 35, TG 7-10,7-11)
Deep cervical fascia components:
5. Locate and describe the specific features of the thyroid gland. (W & B 197-8, N 74, TG 7-13, 7-14)
The thyroid gland is H-shaped with lateral lobes making up the vertical lines and the isthmus making up the middle bar. There also sometimes is a pyramidal lobe which extends upward from the isthmus or from the junction of the isthmus and one of the lateral lobes. The thyroid gland arches over the trachea and is bound posterolaterally by the carotid sheath contents and anterolaterally by the sternothyroid muscles. The upper parts of the lateral lobes are molded against the cricoid and thyroid cartilages.

Thyroid gland:
6. Give the position of the parathyroid glands and consider the thyroid/parathyroid gland relationship in terms of vascular supply and surgical intervention. (W & B 201; N 74, 75, TG 7-14)
The parathyroid glands are usually four (but may be two to six) small glands lying posterior (superior parathyroids) or inferior (inferior parathyroids) to the thyroid gland. Blood supply comes from branches of the inferior or superior thyroid arteries, or from the longitudinal anastomosis between these vessels. Venous drainage flows into the thyroid plexus of veins. Inadvertent removal or damage of the parathyroid glands can occur in surgery on the thyroid gland because of variable positions of the parathyroid glands. If the parathyroid glands atrophy or are all removed during surgery, the patient suffers from tetany, severe convulsive muscle spasms resulting from a fall in serum calcium levels.

Parathyroid gland:
7. Identify and list the parts and branches of the subclavian artery and vein, and describe their course in the neck. (N33, N70, N74, N238, TG7-15A, TG7-15B)
The subclavian artery arises superiorly from the brachiocephalic trunk (right side) or the aortic arch (left side) and travels between the anterior and middle scalene muscles. It then travels inferiorly between the clavicle and first rib to enter the pectoral region, where it becomes the axillary artery. The subclavian artery is divided into three parts by the anterior scalene muscle (this is similar to the pectoralis minor dividing the axillary artery into three parts): The subclavian vein begins at the lateral border of the 1st rib as a continuation of the axillary vein and ends when it unites with the IJV, posterior to the medial end of the clavicle (SC joint). The important part of the subclavian vein is that when it meets the IJV, it forms the brachiocephalic vein. This union is known as the venous angle and is the site where the thoracic duct and right lymphatic duct drain their lymph into the venous circulation. The subclavian vein receives the external jugular vein, anterior jugular vein, and vertebral vein. The external jugular vein receives the suprascapular vein and the transverse cervical vein. One thing to note is that even though the inferior thyroid ARTERY is a branch of the thyrocervical trunk of the subclavian artery, the inferior thyroid VEIN drains into the brachiocephalic vein, separate from the other branches of the thyrocervical trunk, which drain into the subclavian vein.
8. In the root of the neck, locate the vagus and phrenic nerves and describe their relationships to the fascia, vessels, and viscera of the neck. (WB 220; N32, N33, TG7-13 TG7-14)
Vagus nerves - The vagus nerves pass anterior to the first part of the subclavian artery and posterior to the brachiocephalic vein and SC joint to enter the thorax. Higher in the neck, the vagus nerve runs between and posterior to the common carotid artery and the internal jugular vein in the carotid sheath (the artery is medial, the vein lateral). (N31, N32, TG7-13, TG4-45)

Recurrent laryngeal nerves - branches of the vagus nerves - The right recurrent laryngeal nerve loops inferior to the right subclavian artery at approximately the T1 vertebral level. The nerve then ascends in the tracheoesophageal groove to supply all the intrinsic muscles of the larynx, except the cricothyroid (will need to know this later). To better orient yourself, remember that the vagus nerve descends anterior to the subclavian artery and posterior to the vein. The left recurrent laryngeal nerve loops inferior to the arch of the aorta behind the ligamentum arteriosum at approximately the T4/T5 intervertebral disc level. Recurrent nerve ascends in the tracheoesophageal groove to supply all the intrinsic muscles of the larynx, except the cricothyroid (will need to know this later).

Phrenic nerve - arises by a large root from C4 and is reinforced by smaller contributions from C3 and C5. It passes out along the lateral border of the anterior scalene muscle and enters the chest along its medial border. It lies behind the prevertebral layer of deep cervical fascia and is crossed by the transverse cervical and suprascapular vessels. At the root of the neck, the phrenic nerve passes between the first portion of the subclavian vein and subclavian artery and in front of the internal thoracic artery and vein.
9. Describe the anatomy relevant to subclavian vein catheterization: surface landmarks and relationships of the subclavian vein to the clavicle, 1st rib, subclavian artery, brachial plexus, parietal pleura, phrenic and vagus nerves. (N72, N239, N266, TG7-74)
The subclavian vein lies beneath the proximal third of the clavicle. It lies on the first rib anterior to the insertion of the anterior scalene muscle on the scalene tubercle, and it becomes the axillary vein at the lateral border of the first rib. Proximal to the first rib and before its union with the internal jugular vein (which happens behind the sternoclavicular joint), it lies on the cupula, or the dome of cervical parietal fascia. Hence, a needle penetrating the cupula may cause a pneumothorax. Phrenic nerve lies on the anterior surface of the anterior scalene, so it may be impaled here. The subclavian artery lies behind the subclavian vein, and the anterior scalene muscle separates them. The vagus nerve is medial to the anterior scalene and passes between subclavian artery and vein. The roots of the brachial plexus lie behind the subclavian artery.
10. Identify the deep cervical lymph nodes and explain their significance. (N72, N239, N266, TG7-74)
The deep cervical nodes are mostly lateral and posterior to the IJV. The nodes are divided into superior and inferior subgroups at the point where the omohyoid muscle crosses over the IJV. Thus, those deep nodes above this crossing are the superior deep cervical lymph nodes and those below the crossing are the inferior deep cervical lymph nodes. (WB 208) Channels from the inferior deep cervical lymph nodes, also called supraclavicular nodes, join to form the jugular lymphatic trunks, which usually join the thoracic duct on the left side and the right lymphatic duct on the right side (sometimes it will enter the right venous angle directly).
11. Review the arrangement, distribution and function of the cervical sympathetic trunk. (WB 211-12; N 35, 128, 130, 131, 209, TG 7-10, 7-15, 7-95)
The left and right cervical sympathetic trunks: The superior cervical ganglion sends gray rami to C1-C4 spinal nerves (variable) and also gives off other branches. It lies opposite the transverse process of C2. Besides the gray rami to the spinal nerves, branches of the ganglion include: The middle cervical ganglion (which may be absent) sends gray rami to C5-6 spinal nerves. It is at the level of the cricoid cartilage, often close to where the inferior thyroid artery crosses the sympathetic trunk. Besides the gray rami, branches include: The cervicothoracic or stellate ganglion, the fusion of the inferior cervical and first thoracic ganglia, sends gray rami to C6,7,8 and T1. It lies anterior to the transverse process of C7 or the head of rib 1. Its other name, stellate ganglion, comes from the fact that its multiple branches spread out like light rays from a star. Branches include: Functions of the cervical sympathetic trunk: Horner's syndrome involves a lesion of the sympathetic trunk. Two of the more noticeable signs of this syndrome are constriction of the pupil and slight ptosis (drooping) of the eyelid.
12. Review the carotid sheath and contents. (WB 201,203,206; N 32, 33, 35, 125, 126, TG 7-17, 7-18, 7-13, 7-10)
The carotid sheath is a tube-shaped fascia wrapping the common carotid a. and internal carotid a., internal jugular v., and vagus n. Within the sheath, artery is medial, vein lateral, and nerve posterior and between the vessels. The carotid sheath lies anterolateral to the cervical sympathetic trunk, behind the sternocleidomastoid muscle. The sheath blends with the thyroid fascia anteromedially and with the deep surface of sternocleidomastoid anterolaterally. Posteriorly it is attached to prevertebral fascia along the tips of the transverse processes of vertebrae. It ends at the base of the skull where it attaches around the jugular foramen and carotid canal. It is here at the base of the skull that the internal carotid artery and internal jugular vein go their separate ways. Inferiorly, the carotid sheath fuses with scalene fascia, adventitia of great vessels, and the fibrous pericardium.

Through the middle neck levels, the superior root of the ansa cervicalis (from cervical plexus C1-2) lies in the sheath anteriorly. The carotid sheath is posterolateral to the thyroid gland and anterior to the prevertebral fascia. The sympathetic trunk lies behind the medial portion of the sheath. (N 75, TG 7-14,7-15)

The carotid sinus is the dilated terminal part of the common carotid artery, approx. 1 cm long. It is a baroreceptor in the elastic wall which responds to changes in blood pressure. The carotid sinus is innervated by a branch of the glossopharyngeal nerve.

The carotid body is an disc-shaped mass lying behind the bifurcation of the common carotid artery. It has a chemoreceptor sensitive to blood oxygen concentration. The carotid body is innervated by the nerve to carotid sinus from glossopharyngeal nerve, and also receives the nerve to carotid body, a branch of the vagus n. (CN X), as well as sympathetic fibers.
13. List the basic functions of the larynx.
The larynx connects the superior pharynx (oro- and naso-) with the trachea. It is specialized for producing voice, and a special part of the larynx - the epiglottis - protects the airway during swallowing. To achieve these added functions, the larynx has additional cartilages, muscles, ligaments, and mucous membranes.
14. Identify the main cartilages and membranes that form the internal framework (skeleton) of the larynx. (N 65, 66, 77, 78A, 78B, 78C, 78D, 78E, TG 7-22, 7-247-25, 7-28, 7-26, 7-27)
The larynx has nine cartilages (three unpaired and three paired): Membranes of the larynx:
The laryngeal cavity extends superiorly from the laryngeal inlet at the border with the laryngopharynx to the inferior border of the cricoid. It is covered with a mucous membrane, which is continuous with the pharynx above and trachea below. It has three parts.
15. Describe the actions of the intrinsic muscles of the larynx in tensing, relaxing, abducting or adducting the vocal folds. (N 78C, 78D, 79, TG 7-26, 7-27, 7-28)
16. Describe the innervation and vascular supply of the larynx. (N 76, 80, TG 7-26B, 7-26C, 7-28)
Innervation: Vascular supply:
17. Describe the anatomy relevant to cricothyroidotomy: locate the cricothyroid membrane and describe its relationships to the thyroid and cricoid cartilages, vocal cords, cricothyroid artery, and cricothyroid muscles. (N 76, 80, TG 7-26B, 7-26C, 7-28)
The cricothyroid membrane stretches between the thyroid and cricoid cartilages anteriorly. It is partially covered anterolaterally by the cricothyroid muscle. The cricothyroid membrane, but not the muscle, should be incised in a cricothyrotomy. If the incision is midline, the small cricothyroid artery, a branch of the superior thyroid artery, should not be involved, nor should the slender external branch of the superior laryngeal nerve which supplies the cricothyroid muscle and the lower portion of the inferior pharyngeal constrictor. Deep to the cricothyroid membrane, the conus elasticus will be incised in cricothyrotomy, but the vocal cords, which are the thickened upper edges of the conus elasticus, should not be harmed because they connect higher to the inner aspect of the thyroid lamina near the midline.

Questions and Answers:

1. Are the external jugular, anterior jugular, jugular venous arch, and communicating veins bilaterally symmetrical in arrangement or size? Are they all present?
These veins are quite variable and are often asymmetrical. It will be unlikely that you will find all of them in one specimen. (N 31, 256, TG 7-11)
2. How does the innervation to the thyrohyoid muscle differ from the other strap muscles?
Thyrohyoid innervation comes from C1 & C2 via the hypoglossal nerve, arising after the superior root of the ansa cervicalis leaves the hypoglossal nerve. (N 32, 135, TG 7-13, 7-18)
3. Trauma to the external branch of the superior laryngeal nerve to the cricothyroid muscle during thyroid surgery may result in changes in voice quality. Why?
Because cricothyroid muscle tenses the vocal cords by pulling the thyroid and cricoid cartilages closer together anteriorly. (N 74,78, 126, TG 7-26, 7-18)
4. Is there a thyroidea ima artery present?
Only if your cadaver is in the lucky 10% containing this artery.
5. To what vessels do the middle and inferior thyroid veins drain?
Middle thyroid: internal jugular vein
Inferior thyroid: left and right brachiocephalic veins (N 74, TG 7-13)
6. At what foramen on the base of the skull does the internal jugular vein originate?
The internal jugular vein originates at the jugular foramen. (N8, TG7-06)
7. Can you identify the middle cervical ganglion?
This is occasionally absent. When present, it will lie near the level of the inferior thyroid artery and the cricoid cartilage and the transverse process of C6, just anterior to the vertebral artery. (N130, TG7-15)
8 Organize those parts of the cervical sympathetic trunk you have seen so far.
Inferior cervical ganglion - In approximately 80% of people, it fuses with the 1st thoracic ganglion to form the large stellate ganglion (a.k.a. cervicothoracic ganglion). It lies anterior to the transverse process of C7and the neck of the 1st rib on each side and posterior to the origin of the vertebral artery.

Middle cervical ganglion - This is occasionally absent. It lies near the inferior thyroid artery at the level of the cricoid cartilage and the transverse process of C6, just anterior to the vertebral artery.

Superior cervical ganglion - This is a huge ganglion that can be confused with the nodose ganglion of the vagus. This is found at the level of C1 and C2. (N130, N208, TG7-15, TG7-95)
9. Do you see connections (gray rami communicantes) between the trunk or ganglia and spinal nerves?
Yes, but you may NOT see any white rami communicantes because those are only present from T1 through L2. One white ramus reaches the stellate ganglion, only. (N130, TG7-15, TG7-95)
10. Are these (transverse cervical and suprascapular arteries) individual arteries or are they derived from a common trunk?
Both of these arteries should be branches of the thyrocervical trunk which is a branch of the first part of the subclavian artery. Sometimes they arise as a common trunk. Suprascapular vessels travel laterally immediately behind the clavicle, while the transverse cervical arches higher across the posterior triangle. (N33, TG7-15A, TG7-15B)
11. Study its (thyroid gland) relation to the sympathetic trunk and middle cervical ganglion.
The thyroid gland as a whole will be anteromedial to the sympathetic trunk as it ascends on the longus colli muscle. The inferior aspect of the thyroid gland should be just medial to the middle cervical ganglion. (N39, N130, TG7-14)
12. Define the interscalene triangle.
The interscalene triangle is defined as the area between the posterior border of the anterior scalene muscle, anterior border of the middle scalene muscle, and the superior border of the 1st rib. The major structures that are located in this structure are the trunks of the brachial plexus. (N34, TG7-15)
13. In forced inspiration, what muscle raises the second rib?
The posterior scalene muscle, since it inserts onto the second rib. Anterior and middle scalene muscles would effectively raise the second rib also, however they insert on the first rib. (N34, N186, TG7-15)
14. Identify the ascending pharyngeal artery (a branch of the external carotid) distributing to the dorsal wall of the pharynx. Do you find any lymph nodes (retropharyngeal)?
Retropharyngeal lymph nodes are usually present in the tissue between visceral and musculoskeletal parts of the neck, known as the retropharyngeal space, but difficult to find unless they are enlarged by disease. They are associated with the deep cervical nodes found in the carotid sheath just lateral to the space. (N 73, 136, TG 7-74)
15. Define nasal, oral and laryngeal portions of pharynx. What boundaries separate these regions?
The nasopharynx extends from the choanae anteriorly to the soft palate inferiorly; it is the respiratory portion of the pharynx. The oropharynx extends from the soft palate above to the epiglottis below and opens into the mouth anteriorly. The laryngopharynx extends from the epiglottis to the beginning of the esophagus below. It opens into the larynx anteriorly.
16. What structures lie immediately deep (lateral) to the palatine tonsil? Where is the lingual tonsil?
The superior pharyngeal constrictor muscle lies lateral to the palatine tonsil, along with the vessels supplying the tonsil. The lingual tonsil is in the submucosa on the superior surface of the root of the tongue just behind the sulcus terminalis. It is a large collection of lymphoid nodules that give the posterior one-third of the tongue its warty appearance.
17. The cartilages of the larynx along with their articulations and membranes constitute a separate, almost independent, musculoskeletal entity. What structural features differ in male and female?
The thyroid cartilage in male and female are different in shape. In the female, the two thyroid laminae meet in an angle of about 120 degrees. In the male, the thyroid laminae meet at an angle of 90 degrees. Thus the laryngeal prominence (the so called "Adam's apple") in the male is more obvious. The shape as well determines the length of the vocal cords and their consequent pitch; the cords being shorter in women and thus a higher pitched voice.
18. What is the action of the cricothyroid joint?
The cricothyroid muscle brings the arch of the cricoid and the thyroid cartilage together with the pivot at this joint. During this action the vocal folds become more tense and the pitch of the voice increases. Conversely paralysis of this muscle produces hoarseness of voice.
19. What is the glottis?
The glottis is defined as the space between the true vocal folds. It is also called the rima glottidis to differentiate it from the rima vestibuli, the space between the vestibular or false vocal folds.
20. What is the source of the inferior laryngeal nerve and the inferior laryngeal artery?
The inferior laryngeal nerve is the terminal end of the recurrent laryngeal nerve. It is motor to the intrinsic muscles of the larynx, while the recurrent laryngeal supplies the trachea and esophagus as well. The inferior laryngeal artery is a branch of the inferior thyroid artery; it accompanies the nerve into the space deep to the piriform recess.
21. Identify two structures that perforate the thyrohyoid membrane: the internal branch of the superior laryngeal nerve and the superior laryngeal artery. What is the source of each?
The internal branch of the superior laryngeal nerve is a sensory nerve to the interior of the larynx which arises from the vagus. The superior laryngeal artery and vein arise as the first branches of the superior thyroid vessels. (N 69, 74, 126, TG 7-26, 7-28)
22. Does the external branch of the superior laryngeal nerve pass through or give off a branch to the inferior pharyngeal constrictor muscle?
The external branch of the superior laryngeal nerve usually passes through the lower portion of the inferior constrictor muscle (this portion a.k.a. cricopharyngeus m.) supplying it and the cricothryroid muscle. (N 74, 75, 76, TG 7-20, 7-26)