Anatomy of Thyroid Flashcards
Between which vertebrae is the thyroid found?
C5-T1
How many lobes does the thyroid have?
2, they are connected by an isthmus
Which 2 strap muscles are found anterior to the thyroid gland?
Sternohyoid
Sternothyroid
The thyroid is ________ to the thyroid cartilage of the larynx
Inferior
What is the name of the fascia that encircles the thyroid, oesophagus and pharynx?
Pretracheal fascia
Which pharyngeal pouch does the inferior parathyroid gland rise from?
3rd
Which pharyngeal pouch does the superior parathyroid gland rise from?
4th
Which pharyngeal pouch does the superior parathyroid gland rise from?
4th
Where is the oesophagus in relation to the thyroid?
Posterior and medial to the thyroid
What is found lateral to the thyroid?
Carotid sheath
Name the structure in which the thyroid passes as it descends during development
Thyroglossal duct
What clinical significance does the thyroglossal duct have?
Cysts can occur here, which have to be surgically removed
Why is the thyroid highly vascularised?
Its function is to secrete hormones into the blood, therefore needs a good blood supply
Where are the two areas of blood supply targeting the thyroid gland?
1- Superior thyroid arteries branch from the external carotids
2- Inferior thyroid arteries rise from the thyrocervical trunk
Which branch is the superior thyroid from the external carotid artery?
It is the first branch
Which portions of the thyroid gland are supplied by the superior thyroid artery?
The superior and anterior portions
Which portions of the thyroid are supplied by the inferior thyroid artery?
Postero-inferior portions
Which neck muscles are supplied by there thyrocervical trunk?
Scalene muscles
Sternocleidomastoid
Trapezius
Which direction does the superior thyroid artery have to travel to reach the thyroid?
Inferiorly, descends towards thyroid
Which direction does the inferior thyroid artery travel to reach the thyroid?
Super-medially
What percentage of the population will also have the thyroid ima artery?
10%
Where does the thyroid ima artery rise from?
Brachiocephalic trunk
What does the thyroid ima artery supply?
The anterior surface of thyroid and isthmus
Which 3 veins form a plexus to drain the thyroid?
Superior thyroid vein
Middle thyroid vein
Inferior thyroid vein
Which 2 thyroid veins from the plexus that drains the thyroid drain into the internal jugular vein?
Superior + middle
Which thyroid vein from the plexus that drains the thyroid drains into the brachiocephalic vein?
Inferior
Name the nerves that give innervation to the thyroid
Sympathetic trunk
Recurrent laryngeal nerves -> from vagus CNX
Name the vagal nerves that innervate the larynx
Left recurrent laryngeal nerve
Right recurrent laryngeal nerve
Which laryngeal nerve hooks around subclavian artery?
Right recurrent laryngeal artery
Which laryngeal nerve hooks around the arch of the aorta?
Left recurrent laryngeal artery
The recurrent laryngeal nerve hook around the main arteries. Why is this important to consider during surgery on the thyroid?
Have to be careful to not ligate or damage the nerve when near the blood vessels.
Which are the 4 main lymphatic nodes that drain lymph from the thyroid?
Para-tracheal cervical lymph nodes
Para-tracheal lymph nodes
Pre-laryngeal lymph nodes
Tracheal nodes
Which lymph nodes can lymph pass directly into in the drainage of the thyroid gland?
Deep cervical nodes
What are parathyroid glands?
Small endocrine glands that are located in the anterior neck
What is the function of the parathyroid hormone?
Produces parathyroid hormone (control of calcium and phosphate in the body)
Where are the parathyroid glands located?
On the posterior aspect of the lateral lobes of the thyroid
How many parathyroid glands are there?
4
What is the superior parathyroid gland embryonic origin?
4th pharyngeal pouch
What is the inferior parathyroid gland embryonic origin?
3rd pharyngeal pouch
What arteries supply the posterior aspect of the parathyroid gland?
Inferior thyroid arteries
Which arteries contribute to the collateral circulation of the parathyroid glands?
Superior thyroid arteries
Thyroid ima artery
Laryngeal artery
Tracheal artery
Oesophageal artery
Name the 2 lymphatic nodes that the lymph from the parathyroid glands can drain into?
Deep cervical nodes
Para-tracheal lymph nodes
What is the main nervous supply to the parathyroid glands?
Thyroid branches of the cervical sympathetic ganglia
Is endocrine secretion form parathyroids conducted through nerves or hormonally?
Hormonally, the nervous supply is vasomotor, not secretomotor
What could happen if the parathyroid glands have to be removed from the neck during surgery?
It would cause serum levels of calcium to drop significantly, resulting in severe muscle twitches and cramps - could result in death
Remnants of which duct can fill with fluid to form thyroid cysts?
Thyroglossal ducts
What is a lingual thyroid?
Ectopic thyroid tissue that can be located along the route of the thyroglossal duct
What is a goitre?
AN enlarged thyroid gland, produces a swelling that does not rise above the thyroid cartilage
What is the main cause of goitres?
Iodine deficiency
Name other causes of goitres
Congenital hypothyroidism
Autoimmune diseases
Cancers of thyroid
Disorders of hormonal organ system
Why does the goitre not rise above the thyroid cartilage?
The pre tracheal fascia hold it into place
Why does the goitre not rise above the thyroid cartilage?
The pre tracheal fascia hold it into place
Define lymphadenopathy
Enlargement of lymph nodes
Give examples of lymphadenopathies
Chronic tonsillitis
Tuberculosis
Carcinoma
What are branchial cysts and fistulae?
Located in the lateral neck, fluctuant, pain free one sided swellings
Why do branchial cysts occur?
When branchial clefts do not obliterate OR when branchial arches do not fuse properly in embryonic development
Where do branchial cysts usually occur?
On the anterior border of the sternocleidomastoid
