Anatomy of the Thyroid Gland

Question 1

What other structures is the thyroid closely related to?

Answer 1

Larynx and the trachea in the anterior neck

Question 2

What make up the thyroid gland?

Answer 2

Usually consists of two lateral lobes (right and left) and an isthmus (narrow connecting band)

Question 3

Where do the lobes of the thyroid attach?

Answer 3

Later aspects of the thyroid and cricoid cartilages, and to the trachea

Question 4

Where is the isthmus located?

Answer 4

Lies anterior to the second and third cartilages of the trachea

Question 5

How does a lump in the thyroid/enlarged thyroid gland move when swallowing?

Answer 5

Moves superiorly then inferiorly with the larynx = due to its relationship with the larynx and the trachea

Question 6

Where are the four parathyroid glands located?

Answer 6

Located on the posterior surfaces of the thyroid gland’s lateral lobes (superior and inferior on each side)

Question 7

What are some features of the pyramidal lobe?

Answer 7

Mean prevalence of 44.6%, most commonly originates from the left lateral lobe, < 10% aren’t connected to main thyroid gland, most attach superiorly to thyroid cartilage, may extend as far superiorly as the hyoid bone

Question 8

What does the thyroid gland begin its development as?

Answer 8

Midline epithelial proliferation at the junction between the anterior 2/3 and the posterior 1/3 of the tongue (foramen caecum in adult)

Question 9

Where does the thyroid gland migrate to during its development?

Answer 9

Migrates inferiorly whilst remaining attached to the tongue via the thyroglossal duct

Question 10

When does the thyroid gland reach its final position in relation to the larynx and trachea?

Answer 10

In the seventh week of development = thyroid is at C7 vertebral level

Question 11

What can block the migratory path of the thyroid during its development?

Answer 11

Thyroglossal duct cysts or ectopic thyroid tissue

Question 12

Where are the platysmal muscles located?

Answer 12

Immediately deep to the skin within the superficial fascia of the neck

Question 13

What group of muscles do the platysmal muscles belong to?

Answer 13

Muscles of facial expression = innervated by facial nerve (CN VII)

Question 14

What are the different fascial compartments of the neck?

Answer 14

Prevertebral (deep) fascia, investing fascia, carotid sheaths (x2), pretracheal fascia

Question 15

Where is the prevertebral (deep) fascia located?

Answer 15

Located posteriorly = encloses postural neck muscles and cervical vertebrae

Question 16

What does the investing fascia envelope?

Answer 16

All the other neck fascial compartments, also encloses trapezius and sternocleidomastoid muscles

Question 17

What are the contents of the carotid sheaths?

Answer 17

Located anterolaterally = encloses deep vagus nerves, deep cervical lymph nodes, common then internal carotid arteries, internal jugular vein

Question 18

What does the pretracheal fascia enclose?

Answer 18

Located anteriorly = oesophagus, trachea, thyroid gland, strap muscles, recurrent laryngeal nerves

Question 19

Where does the descending part of the trapezius muscle attach?

Answer 19

Attaches inferiorly to the spine of the scapula and the lateral end of the clavicle

Question 20

What are the attachments of the sternocleidomastoid muscle?

Answer 20

Sternal head = attaches to manubrium of sternum

Clavicular head = attaches to medial end of clavicle

Question 21

Where do both heads of the sternocleidomastoid muscle pass?

Answer 21

Pass superiorly to attach to the mastoid process of the temporal bone

Question 22

What are the carotid sheaths?

Answer 22

Bilateral tubes of deep fascia = located deep to the investing fascia and located anterolaterally in the neck on either side of the thyroid gland

Question 23

What are the attachments of the carotid sheaths?

Answer 23

Superior = attaches to base of the skull (around jugular foramen and entrance to carotid canal)
Inferiorly = blends with mediastinal fascia

Question 24

What is the lymphatic drainage of the thyroid gland?

Answer 24

Drains from superior deep cervical lymph nodes into inferior deep cervical lymph nodes (left and right)

Question 25

Where is lymph on the right side of the body returned to?

Answer 25

Right venous angle via the right lymphatic duct

Question 26

Where is lymph from the left side of the body returned to?

Answer 26

Left venous angle via the thoracic duct

Question 27

What nodes make up the tracheal lymph nodes?

Answer 27

Pretracheal and paratracheal nodes

Question 28

Where do the vagus nerves arise from?

Answer 28

Branch from the medulla oblongata = exit skull via jugular foramen and descend through in carotid sheath

Question 29

Where are the vagus nerves located in the chest?

Answer 29

Right is lateral to trachea Left is on left side of aortic arch Both are posterior to lung hilum and on the oesophagus

Question 30

What do the vagus nerves pass through the diaphragm with?

Answer 30

The oesophagus

Question 31

Where do the vagus nerves divide into their terminal branches?

Answer 31

On surface of the stomach = supply the abdominal organs with parasympathetic axons to the distal midgut

Question 32

What does recurrent mean when applied to nerves?

Answer 32

They turn back in the opposite direction

Question 33

Where do the recurrent laryngeal nerves recur?

Answer 33

``` Right = recurs under subclavian artery Left = recurs under arch of the aorta ```

Question 34

What is the embryological origin shared by the arch of the aorta and right subclavian artery?

Answer 34

The fourth aortic arch artery

Question 35

What are the strap muscles?

Answer 35

Thyrohyoid, sternothyroid, sternohyoid and omohyoid muscles

Question 36

Where do the thyrohyoid and sternohyoid muscles attach?

Answer 36

``` Thyrohyoid = attaches from hyoid to thyroid Sternohyoid = attaches from hyoid to sternum ```

Question 37

Where do the sternothyroid and omohyoid muscles attach?

Answer 37

``` Sternothyroid = attaches from thyroid to sternum Omohyoid = attaches from hyoid to shoulder (has superior and inferior bellies) ```

Question 38

What attaches the intermediate tendon of the omohyoid to the clavicle?

Answer 38

The fascial sling

Question 39

What are some surgical methods used to operate on the thyroid gland?

Answer 39

Classical thyroidectomy, endoscopically assisted thyroidectomy, endoscopic trans-axillary approach, endoscopic trans-breast approach

Question 40

What is the classical thyroidectomy incision?

Answer 40

A collar incision is made within the natural skin crease or in the direction of Langer's lines

Question 41

What are some requirements of the incision made during a classical thyroidectomy?

Answer 41

Incision should be just superior to the clavicles and jugular notch, and should be made through the skin and platysma

Question 42

What can cause paralysis of the vocal cord?

Answer 42

Injury to the recurrent laryngeal nerve

Question 43

What does unilateral injury to the recurrent laryngeal nerve cause?

Answer 43

Hoarseness or weakness of the voice and a weak cough

Question 44

What does bilateral injury to the recurrent laryngeal nerve cause?

Answer 44

Aphonia = inability to produce sound | Inability to close the rima glottidis to prevent aspiration or produce a good cough

Question 45

What separates the carotid sheaths?

Answer 45

The alar fascia