The Neck

Question 1

What is the omohyoid muscle? Label its location

Answer 1

INFRAHYOID
Omohyoid has an inferior and superior belly. The inferior is comes from the scapula and joins the superior which comes from the clavicle, which then ascends to attach to the hyoid. It acts to depress the hyoid bone. Innervated by anterior rami of C1-C3.

Question 2

What is the sternohyoid muscle? Label its location

Answer 2

INFRAHYOID
Originates from the sternum and sternoclavicular joint. It inserts onto the hyoid bone. Acts to depress the hyoid bone. Innervated by anterior rami of C1-C3.

Question 3

What is the sternothyroid muscle? Label its location

Answer 3

INFRAHYOID
Originates from the manubrium of the sternum and attaches to the thyroid cartilage. Acts to depress the thyroid cartilage. Innervated by anterior rami of C1-C3.

Question 4

What is the thyrohyoid mohyoid muscle? Label its location

Answer 4

INFRAHYOID
Originates from the thyroid cartilage of the larynx and attaches to the hyoid bone. Acts to depress the hyoid bone. Innervated by anterior rami of C1-C3.

Question 5

What is the ansa cervicalis?

Answer 5

The ansa cervicalis is a loop of nerves, formed by nerve roots C1-C3. It gives off four muscular branches:
Superior belly of the omohyoid muscle
Inferior belly of omohyoid muscle
Sternohyoid
Sternothyroid
These muscles (the infrahyoids) act to depress the hyoid bone; an important function for swallowing and speech.

Question 6

What is the sternocleidomastoid muscle? Label its location

Answer 6

One of the largest and most superficial cervical muscles. Originates from the manubrium and the clavicle. Inserts onto the mastoid process of the temporal bone. Acts in rotation of the head to the opposite side and flexion of the neck. Innervated by the accessory nerve.

Question 7

What is the platysma muscle? Label its location

Answer 7

A superficial muscle that overlaps the sternocleidomastoid. Originates from the skin/fascia of infra- and supraclavicular regions. Inserts onto the lower border of mandible, skin of buccal/cheek region, lower lip, Orbicularis oris muscle. Innervated by the cervical branch of the facial nerve. Acts to depress the mandible and angle of mouth, tenses skin of lower face and anterior neck.

Question 8

What is the thyroid gland?

Answer 8

An endocrine gland located in the anterior neck, spanning between C5-T1. Wraps around the cricoid cartilage. Lies in front of the larynx and trachea (2nd to 4th tracheal rings) and behind the sternohyoid and sternothyroid muscles.
Secretes thyroxine (T4) and triiodothyronine (T3) which control the body’s metabolic rate and protein synthesis.
Divided into two lobes, connected by an isthmus.

Question 9

What is the blood supply of the thyroid?

Answer 9

Supplied by the superior and inferior thyroid arteries, paired arteries on both left and right.
Superior thyroid artery is the first branch from the external carotid artery and supplies the superior and anterior portions of the gland.
Inferior thyroid artery arises from the thyrocervical trunk (a branch of the subclavian artery) and supplies the posterior and inferior portions of the gland.

Question 10

How is the thyroid gland innervated?

Answer 10

The gland receives sympathetic nerve supply from the superior, middle and inferior cervical ganglion of the sympathetic trunk. The gland receives parasympathetic nerve supply from the superior laryngeal nerve and the recurrent laryngeal nerve.

Question 11

What is the venous drainage of the thyroid?

Answer 11

Venous drainage is carried out by the superior, middle and inferior thyroid veins, which form a venous plexus. The superior and middle veins drain into the internal jugular veins, whereas the inferior drains into the brachiocephalic vein.

Question 12

What are the parathyroid glands?

Answer 12

Small endocrine glands located in the anterior neck. They are responsible for the production of parathyroid hormone, which acts to control calcium levels in the body.
Located on the posterior aspect of the lateral lobes of the thyroid gland. They are flattened and oval in shape, situated external to the gland itself, but within its sheath.
Usually 4 parathyroid glands:
Superior parathyroid glands: Derived embryologically from the fourth pharyngeal pouch
Inferior parathyroid glands: Derived embryologically from the third pharyngeal pouch

Question 13

What is the blood supply to the parathyroid glands?

Answer 13

The posterior aspect of the thyroid gland is supplied by the inferior thyroid arteries. Thus its branches also supply the nearby parathyroid glands. Collateral circulation is delivered by the superior thyroid arteries, thyroid ima artery, and laryngeal, tracheal and oesophageal arteries.

Question 14

What is the venous drainage of the parathyroid glands?

Answer 14

The parathyroid veins drain into the thyroid plexus of veins.

Question 15

What are the extrinsic muscles of the larynx?

Answer 15

The extrinsic muscles of the muscles include the suprahyoid and infrahyoid groups, and the stylopharyngeus (a muscle of the pharynx). The suprahyoid muscles and the stylopharyngeus elevate the larynx, whilst the infrahyoid muscles depress the larynx.

Question 16

What is the carotid sheath and where is it located?

Answer 16

Carotid sheath is is one of four accumulations of deep cervical fascia or fibrous connective tissue of the neck which surrounds the great vessels of the neck. It starts bilaterally at the level of the oropharynx beneath the sternocleidomastoid muscle. It joins up medially with the prevertebral fascia and communicates inferiorly with the mediastinum.
The four major structures contained in the carotid sheath are: the common carotid artery as well as the internal carotid artery (medial) internal jugular vein (lateral) the vagus nerve (CN X) (posterior) the deep cervical lymph nodes.

Question 17

What does the carotid sheath house?

Answer 17

Within the sheath, there is the common carotid artery, the internal carotid artery, the internal jugular vein, the vagus nerve. There are also deep cervical lymph nodes and sympathetic nerve fibres.

Question 18

What is the recurrent laryngeal nerve?

Answer 18

The recurrent laryngeal nerve (RLN) is a branch of the vagus nerve (cranial nerve X) that supplies all the intrinsic muscles of the larynx, with the exception of the cricothyroid muscles which is innervated by the external branch of the superior laryngeal nerve.. There are two recurrent laryngeal nerves, right and left.

Question 19

What is the pathway of the left recurrent laryngeal nerve?

Answer 19

The left laryngeal nerve, which is longer, branches from the vagus nerve to loop under the arch of the aorta, posterior to the ligamentum arteriosum before ascending.

Question 20

What is the pathway of the right recurrent laryngeal nerve?

Answer 20

The right branch loops around the right subclavian artery. As the recurrent nerve hooks around the subclavian artery or aorta, it gives off several cardiac filaments to the deep part of the cardiac plexus.

Question 21

What is the thyroid cartilage? Label its location

Answer 21

The thyroid cartilage is a large structure that is made up of two sheets which join together to form the laryngeal prominence (Adam’s apple in adult males). Posteriorly its made up of the superior and inferior horns which connect to the hyoid bone.

Question 22

What is the cricoid cartilage? Label its location

Answer 22

The cricoid cartilage is a complete ring of hyaline cartilage, with a broad sheet at the back and a narrow arch at the front. At the level of C6. It articulates with the inferior horns of the thyroid cartilage and the paired arytenoid cartilages posteriorly.

Question 23

What is the epiglottis?

Answer 23

The epiglottis is a leaf shaped plate of elastic cartilage which marks the entrance to the larynx. Its ‘stalk’ is attached to the back of the anterior aspect of the thyroid cartilage. During swallowing, the epiglottis flattens and moves posteriorly to close off the larynx and prevent aspiration.

Question 24

What are the arytenoid cartilages?

Answer 24

The arytenoid cartilages are pyramidal shaped structures that sit on the cricoid cartilage. They consist of an apex, base, three sides and a vocal and muscular process, and provides an attachment point for various key structures in the larynx.

Question 25

What are the corniculate cartilages?

Answer 25

The corniculate cartilages are minor cartilaginous structures. They articulate with the apices of the arytenoid cartilages.

Question 26

What are the cuneiform cartilages?

Answer 26

The cuneiform cartilages are located within the ary-epiglottic folds. They have no direct attachment, but act to strengthen the folds.

Question 27

How to differentiate between lumps in the neck?

Answer 27

To check the location of the lump, lumps in the thyroid will elevate with swallowing but lumps in the lymph nodes will not.

Question 28

Where would you create an emergency airway?

Answer 28

Between the thyroid and cricoid cartilage, through the cricothyroid membrane.

Question 29

Why does the thyroid needs such a good blood supply?

Answer 29

Iodine is present in very low concentration in the blood so the gland needs a high blood flow to ensure adequate delivery of iodine.

Question 30

Which structure may be compressed by an enlarged thyroid gland?

Answer 30

The trachea

Question 31

Why might a patient develop hypocalcaemia after thyroid surgery?

Answer 31

The parathyroid glands may be (accidentally or deliberately) removed during thyroid surgery which will cause acute (sudden) hypoparathyroidism.