Anatomy of the thyroid and parathyroid glands

Question 1

What are the main parts of the thyroid gland ?

Answer 1

Has two lobes connected by the isthmus

Question 2

Describe the location of the thyroid gland

Answer 2

• Sits anterior to the layrnx & trachea
• The lobes of the thyroid attach to the lateral aspects of the thyroid and circoid cartilages
• Isthmus of the thyroid gland sits anterior to the 2nd and 3rd cartilages of the trachea

Question 3

Due to the close anatomical relationship of the thyroid gland and the Larynx/trachea - what happens to the thyroid gland upon swallowing ?

Answer 3

It moves up superiorly

Question 4

Where are the parathyroid glands located ?

Answer 4

Located on the posterior surfaces of the thyroid gland’s lateral lobes

Question 5

In some patients there may be the presence of a pyramidal lobe of the thyroid what is this ?

Answer 5

• As the thyroid descends during development it passes through the thyroglossal duct.
• However in some people the duct continues as the pyramidal lobe attaching to the thyroid (essentially just an extra bit of thyroid tissue)

Question 6

Describe the basic embryology of the thyroid gland

Answer 6

1. Thyroid begins development as a midline epithelial proliferation at the junction between the anterior 2/3rds and posterior 1/3rd of the tongue
2. Then migrates inferiorly via thyroglossal duct
3. Reaches final position in front of larynx/trachea in the 7th week of development

Question 7

Where are the platysma muscles located ?

Answer 7

Located immediately deep to the skin of the neck in the superficial fascia (belong to the muscles of fascial expression)

Question 8

How can infection spread from the neck into the mediastinum ?

Answer 8

It can spread down to the mediastinum within the fascial planes between the layers of deep cervical fascia

Question 9

Describe the attachments of the sternocloidomastoid muscle

Answer 9

• Attaches to the manubrium of the sternum and clavicular head of the clavicle
• Then attaches the mastoid process of the temporal bone

Question 10

Describe the attachments of the trapezius muscle

Answer 10

• Inferiorly - spine of scapula and lateral end of clavicle
• Superiorly - occipital bone

Question 11

Where are the carotid sheaths located in the neck ?

Answer 11

Deep to the investing fascia & located anterolaterally in the neck either side of the thyroid gland

Question 12

What is contained in the carotid sheath ?

Answer 12

• The internal jugular vein
• The common, then the internal carotid arteries
• The vagus nerve
• The deep cervical lymph nodes

Question 13

Describe the blood supply to the thyroid gland

Answer 13

The anterior and superior aspect of the thyroid gland is supplied by the left and right superior thyroid artery, which is a branch of the external carotid arteries

The inferior and posterior aspect of the thyroid gland is supplied by the left and right inferior thyroid arteries, which are branches of the L and R subclavian arteries

Question 14

Describe the blood supply to the parathyroid gland

Answer 14

The posterior aspect of the thyroid gland is supplied by the inferior thyroid arteries. Thus its branches also supply the nearby parathyroid glands.

Question 15

Describe the venous drainage of the thyroid and parathyroid glands

Answer 15

• Thyroid - superior, middle and inferior thyroid veins, which form a venous plexus.
• Parathyroid - drains into the thyroid plexus of veins

Question 16

What is the lymphatic drainage of the thyroid and parathyroid glands ?

Answer 16

The lymphatic vessels of the parathyroid glands drain (along with those of the thyroid gland) into the deep cervical lymph nodes and paratracheal lymph nodes.

Question 17

Describe the route of the vagus nerve CN X

Answer 17

• Connects with the medulla oblongata
• Passes through the jugular foramen
• Descends through the neck in the carotid sheath
• Gives off 2 branches in the larynx and neck - 1. superior laryngeal nerve and 2. right recurrent laryngeal nerve
• 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 18

In the chest what is the other branch of the vagus nerve given off ?

Answer 18

The left recurrent laryngeal nerve by the the left vagus nerve

Question 19

Recurrent means to turn back on itself - where does the left and right recurrent laryngeal nerves turn back on themselves ?

Answer 19

• Left - hooks under the arch of the aorta and turns back on itself
• Right - hooks under the subclavian artery and turns back on itself

Question 20

What are the close anatomical relations of the thyroid gland ?

Answer 20

Question 21

What are the infrahyoid (strap) muscles of the neck ?

Answer 21

A group of four muscles that are located inferiorly to the hyoid bone in the neck.

• Superficial - omohyoid and sternohyoid
• Deep - thyrohyoid and sternothyroid

Question 22

What are the boundaries of the anterior triangle of the neck ?

Answer 22

• Superiorly – Inferior border of the mandible (jawbone)
• Laterally – Medial border of the sternocleidomastoid
• Medially – Imaginary sagittal line down midline of body

Question 23

What are the boundaries of the posterior triangle of the neck ?

Answer 23

• Anterior: Posterior border of the SCM.
• Posterior: Anterior border of the trapezius muscle.
• Inferior: Middle 1/3 of the clavicle.

Question 24

What are the signs and symptoms of unilateral and bilateral recurrent laryngeal nerve injury ?

Answer 24

Recurrent nerve injury results in paralysis of the vocal cord

Unilateral injury causes “hoarseness” or weakness of the voice & a weak cough

Bilateral injury causes aphonia (inability to produce sound) & inability to close the rima glottidis (opening between vocal cords) to prevent aspiration (inhalation of foreign body into the lungs) or to produce a good cough (requires closure of the rima glottidis)