Anatomy of the thyroid gland

Question 1

Which structures in the anterior neck is the the thyroid gland closely related to?

Answer 1

The larynx and trachea

Question 2

What does the thyroid gland consist of?

Answer 2

2 lateral lobes and an isthmus ( a narrow connecting band)

Question 3

What do the lobes of the thyroid gland attach to?

Answer 3

The lateral aspects of the cricoid and thyroid cartilages and to the trachea.

Question 4

Where does the isthmus lie in relation to the trachea?

Answer 4

It lies anterior to the 2nd and 3rd cartilages of the trachea.

Question 5

What is an enlarged thyroid gland called?

Answer 5

A goitre

Question 6

Where are the parathyroid glands located?

Answer 6

On the posterior surfaces of the thyroid gland’s lateral lobes.

Question 7

How are the 4 parathyroid glands named?

Answer 7

Right/left superior/inferior parathyroid gland

Question 8

What is the prevalence of the pyramidal lobe of the thyroid gland?

Answer 8

28-55 % (mean 44.6%)

Question 9

Which lobe of the thyroid gland does the pyramidal lobe most commonly originate?

Answer 9

The left lateral lobe

Question 10

Is the pyramidal lobe always connected to the main thyroid gland?

Answer 10

No- 9.2% are not

Question 11

Where do most pyramidal lobes of the thyroid gland attach superiorly?

Answer 11

To the thyroid cartilage

Question 12

How far superiorly can a pyramidal lobe of the thyroid gland extend?

Answer 12

As far as the hyoid bone

Question 13

a) How does the thyroid gland develop?

b) What evidence is there for this in the adult?

Answer 13

a) As a midline epithelial proliferation at the junction between the anterior 2/3rds (oral/horizontal part) and the posterior 1/3rd (oropharyngeal/vertical part) of the tongue.
The gland migrates inferiorly whilst remaining attached to the tongue via the thryoglossal duct. The gland reaches its final position in relation to the larynx/trachea in the 7th week of development.
b) Foramen caecum- may still be patent in some adults.

Question 14

What may be located at any position in the migratory path of the thyroid?

Answer 14

Ectopic thyroid tissue

Thyroglossal duct cysts

Question 15

a) Name the muscles located immediately deep to the skin within the superficial fascia of the neck.
b) What group of muscles do they belong to?
c) What is the nerve supply to the muscles?

Answer 15

a) The platysma muscles
b) The muscles of facial expression
c) Cranial nerve VII (the facial nerve)

Question 16

What muscle type are platysma muscles?

Answer 16

Skeletal muscles

Question 17

How is the deep cervical fascia arranged?

Answer 17

In tubes

Question 18

Describe the investing deep fascia in the neck (i.e. what it is deep to and what it encloses).

Answer 18

It is deep to the superficial fascia.
It encloses all the other neck fascial compartments.
It encloses two pairs of muscles: trapezius and sternocleidomastoid

Question 19

Describe the prevertebral deep fascia (i.e. what it is deep to, where it is located and what it encloses)

Answer 19

It is deep to the investing fascia

It is located posteriorly and encloses the cervical vertebrae and the postural neck muscles.

Question 20

Describe the carotid sheaths (i.e. what they are deep to, where they are located and what they enclose)

Answer 20

The carotid sheaths are deep to the investing fascia
They are located anterolaterally
They enclose:
The internal jugular veins
The carotid arteries
The vagus nerves
The deep cervical lymph nodes

Question 21

Describe the pretracheal (deep) fascia (i.e. what it is deep to, where it is located and what it encloses)

Answer 21

It is deep to the investing fascia
It is located anteriorly
It encloses:
The strap muscles
The thyroid gland
The trachea
The oesophagus 
The recurrent laryngeal nerves

Question 22

How can infection spread in the neck?

Answer 22

It can spread in the planes between the fascial tubes

Question 23

Where is the retropharyngeal space?

Answer 23

Between the pretracheal and prevertebral fascia.

Question 24

What are the attachments of the sternocleidomastoid muscle?

Answer 24

The sternal head attaches to the manubrium of the sternum
The clavicular head attaches to the medial end of the clavicle
Both heads pass superiorly to attach to the mastoid process of the temporal bone.

Question 25

Name two superficial veins in the neck and where they drain into.

Answer 25

The anterior jugular vein: drains into the external jugular vein
The external jugular vein: drains into the subclavian vein.

Question 26

Name the arteries which supply the thyroid and parathyroid glands, and state which arteries they are branches of.

Answer 26

Left and right superior thyroid arteries: branches of the external carotid arteries
Left and right inferior thyroid arteries: branches of the subclavian arteries

Question 27

Name the veins which drain blood from the thyroid and parathyroid glands and state which veins they drain into.

Answer 27

Left and right superior thyroid veins: Drain into left/right internal jugular veins
Left and right middle thyroid veins: Drain into the left/right internal jugular veins
Left and right inferior thyroid veins: Drain into the left brachiocephalic vein

Question 28

Name the lymph nodes surrounding the thyroid gland.

Answer 28

Left/right superior deep cervical nodes
Left/right inferior deep cervical nodes
Pretracheal node
Paratracheal nodes

Question 29

Which somatic branches to the larynx of the vagus nerve occur in the neck?

Answer 29

Superior laryngeal nerve

Right recurrent laryngeal nerve

Question 30

What structure encloses the vagus nerve as it passes through the neck?

Answer 30

The carotid sheath

Question 31

Describe the course of the right vagus nerve in the chest

Answer 31

Descends on the right lateral aspect of the trachea
Posterior to the lung root
Onto the oesophagus

Question 32

Describe the course of the left vagus nerve in the chest

Answer 32

Left side of arch of the aorta
Gives the left recurrent laryngeal nerve
Posterior to the left lung root
Onto the oesophagus

Question 33

Describe the course of both vagus nerves in the abdomen

Answer 33

Both vagus nerves pass through the diaphragm with the oesophagus and divide into their terminal branches on the surface of the stomach
Supply the abdominal organs with parasympathetic axons to the distal midgut.

Question 34

Name the strap muscles and their attachments.

Answer 34

Omohyoid: hyoid to shoulder (has inferior and superior belly)
Sternothyroid: sternum to thyroid
Sternohyoid: sternum to hyoid
Thyrohyoid: thyroid to hyoid

Question 35

Which bone is the intermediate tendon of omohyoid attached to by a fascial sling?

Answer 35

Clavicle

Question 36

What are the surgical approaches to the thyroid gland?

Answer 36

Classical thyroidectomy
Endoscopically assisted thyroidectomy
Endoscopic trans-axillary approach
Endoscopic trans-breast approach

Question 37

What incision is made in a classical thyroidectomy incision?

Answer 37

A “collar” incision is made within a natural skin crease or in the direction of Langer’s lines
Just superior to the clavicles and jugular notch
The incision is made through skin and platysma

Question 38

What does recurrent laryngeal nerve injury result in?

Answer 38

Paralysis of the vocal cord
can be unilateral or bilateral
Unilateral injury causes hoarseness or weakness of the voice and a weak cough
Bilateral injury causes aphonia and inability to close the rima glottidis to prevent aspiration or to produce a good cough