Anterior triangle of the neck

Question 1

What are pathologies of the thyroid?

Answer 1

Goitre, penetrating trauma.

Question 2

Where would you insert a central cathater?

Answer 2

Anterior triangle. Between the two distal heads of the sternocleidomastoid into the internal jugular vein.

Question 3

Why is the anatomy of the anterior triangle important?

Answer 3

To perform tracheostomy/cricothyroiditomy. Have to avoid the thyroid (sits on top of tracheal cartilage 2 and 3) because it will bleed a lot.

cricothyroiditomy - between the thyroid cartilage and the cricoid cartilage

tracheostomy - need to remove the isthmus of the thyroid gland and go through the first and second or second and third trachea cartilage.

Question 4

Where is the anterior triangle?

Answer 4

Anterior to the anterior border of the sternocleidomastoid muscle
Down the midline of the neck is the anterior border.
Superior border is the inferior border of the mandible.

Question 5

What veins are in the supeficial layer of the anterior neck?

Answer 5

The anterior jugular veins.

Question 6

What are the muscles in the anterior triangle?

Answer 6

Four Infrahyoid muscles (strap muscles; inferior to hyoid bone)

1. Sternohyoid - runs between the sternum and they hyoid bone (runs directly superficial to the following two muscles)
2. Sternothyroid - sternum to the thyroid cartilage
3. thyrohyoid - thyroid cartilage to the hyoid bone
4. Omohyoid - between hyoid bone and the shoulder - sits deep and lateral to sternohyoid - the anterior belly of the omohyoid is in the anterior triangle and the posterior belly is in the posterior triangle.

Question 7

What is the cervical plexus, what are the cranial roots and what muscles does it innervate?

Answer 7

C1-C4
Motor and sensory
Loop called ansa cervicalis (only motor, C1 - C3 )
The ansa cervicalis innervates the infrahyoid muscles.

The ansa cervicalis has a superior and an inferior root. The superior root is innervated by C1 and the inferior root is innervated by C2 and C3.

Superior root of ansa cervicalis - innervates thyrohyoid (C1)
Inferior root of ansa cervicalis innervates omohyoid, sternothyroid and sternohyoid (C2 and C3)

Also contains the transverse cervical, the great auricular nerve and the lesser occipital nerve (all sensory)

Question 8

Where is the thyroid and what are the components?

Answer 8

Just deep to the pretracheal fascia (deep to the infrahyoid muscles). It has two lateral lobes and the connecting isthmus. The isthmus sits on top of the second and third tracheal cartilage.

The lateral lobes may go up to the upper border of the thyroid cartilage.

Question 9

Where does the isthmus of the thyroid sit?

Answer 9

The isthmus sits on top of the second and third tracheal cartilage.

Question 10

What are the names of the cartilage around the thyroid gland?

Answer 10

Thyroid cartilage then cricoid cartilage then trachea cartilage

Question 11

What is the blood supply to the thyroid gland?

Answer 11

Two supplies to the upper and lower poles of the lateral lobe.

The superior thyroid artery branch of the external carotid

Inferior thyroid artery from the thyrocervical trunk.

In 30% there is another artery that supplies the isthmus that comes directly from the arch of the aorta called the ima.

Question 12

What is the venous drainage to the thyroid gland? Where would you look for metastasis if a tumour was in the superior or inferior parts.

Answer 12

Superior, middle and inferior thyroid veins.

The superior and middle thyroid veins drain into the internal jugular vein and the inferior thyroid vein drains into the brachiocephalic. Both left and right inferior thyroid veins drain into the left brachiocephalic.

Question 13

What is the lymphatic drainage for the thyroid gland?

Answer 13

They drain to the paratracheal and deep cervical lymph nodes

Question 14

What is the innervation of the thyroid gland?

Answer 14

Sympathetic: middle cervical ganglion (runs with arteries)
Parasympathetic: vagus (recurrent laryngeal nerve)

Question 15

Where does the sympathetic nerves come out of the vertebrae and how is the neck innervated by the sympathetics?

Answer 15

T1-L2 - sympathetic chain

Three cervical ganglions in the nck. Superior, middle and inferior cervical ganglion

Question 16

What tissues are around the thyroid gland and what structures do you need to watch out for if you are removing one lobe of the thyroid?

Answer 16

Behind the isthmus is the tracheal cartilage (2 and 3). The trachea. Behind that is the oesophagus with the recurrent laryngeal nerves on either side between the trachea and oesophagus. More laterally you have the carotid sheath with the internal jugular vein, common carotid and vagus nerve. The stap (infrahyoid) muscles are anterior.

If you need to remove a lobe of the thyroid you need to watch out for the common carotid, the recurrent laryngeal nerve

Question 17

What is the embryology of the thyroid and what are some defects in development?

Answer 17

In the embryo the buds of the thryoid forms in the foramen cecum, which is behind the tongue.
The thyroid gradually moves down to the final destination (above the jugular notch) by going through the thyroglassal duct.

In some cases, some tissue stays within the between the tongue and the final position.
If the tissue stays within by the tongue it is called lingual thyroid.
If it is between the tongue and the hyoid bone it is accessory thyroid tissue.
If it between the hyoid and the final position it is called cervical thryroid.
If you have extra tissue on top of the normal thyroid then it is pyramidal thyroid.

In some people the thyroglossal duct may not close and so food that is being eaten may enter

Question 18

What are the suprahyoid muscles?

Answer 18

These are the muscles above the hyoid bone.
The most superficial is the anterior belly of diagastric. In the same plane is the posterior belly of diagastric and the stylohyoid.
The posterior belly of diagastric origionates from the mastoid process and the tendon goes through a tendon and joins the anterior belly of diagastric which attaches to the posterior mandable.

Stylohyoid origionates from the styloid process and binds to the hyoid bone.

Deep to the anterior belly of diagastric is the mylohyoid muscle. which is the pelvis of the oral cavity.

Deep to the myolohyoid is the geniohyoid..

Question 19

What is the innervation of the suprahyoid muscles?

Answer 19

Between the styloid and mastoid process is the stylomastoid formaen that the facial nerve exits through and this innevates the posterior belly of diagastric and stylohyoid.

The anterior belly of diagastric and mylohyoid are innervated by V3.

The geniohyoid is innervated by C1 (superior root of ansa cervicsalis)

Question 20

What is the arterial supply to the neck?

Answer 20

External carotid - not the internal carotid (no branch in the neck).
If you see a branch off a carotid artery it must be the external carotid. These branches are the superior thyroid artery, lingual artery and facial artery.

Question 21

What is the venus drainage of the neck?

Answer 21

Internal and external jugular vein.

Question 22

What forms the external jugular vein?

Answer 22

The posterior auricular vein and the retromandibular veins form the external jugular.

Question 23

What forms the internal jugular?

Answer 23

The sigmoid sinus

Question 24

Where does the vagus nerve exit the skill, travel through, what happens at the root of the neck and what are the branches it gives off?

Answer 24

It exits the skull through the jugular foramen between CNIX and CNXI. It travels downward in the carotis sheeth between the internal carotid artery and the internal jugular vein.
At the root of the neck it passes in fromt of the subclavian artery and behind the subclavian vein to enter the mediastinum.
The vagus gives of the recurrent laryngeal branches

Question 25

Where does the glossopharyngeal nerve run?

Answer 25

It leaves the skull through the jugular foramen and lies deep to the styloid apparatus. It then runs down and forward between the intetrnal and external carotid arteries, curves around the lateral border of stylopharyngeus and continues in an anterior direction to reach the base of the tongue.

Question 26

Where does the accessory nerve run?

Answer 26

It leaves the skull through the jugular foramen, posterior to CNX, crosses the transverse process of the atlas and passes medial to the styloid process and posterior belly of diagastric to perforate the sternocleidomastoid muscle and reach the posterior triangle of the neck.

Question 27

Where does the hypoglossal nerve run?

Answer 27

It leaves the skull through the hypoglossal foramen, passes between the internal carotid artery and internal jugular vein. It then crosses three arteries, occipital, external carotid and lingual arteries deep to the posterior belly of diagastric to reach the tongue. A branch from the anterior rami of C1 hitchhikes with it. This branch innervates some of the suprahyoid muscles (thyrohyoid and geniohyoid)