Thyroid glands and hormones Flashcards
What is the isthmus (the narrow part) of the thyroid gland in line with in the neck
1st tracheal cartilage
Which triangle in the neck is the thyroid gland found
Lower anterior
Where are the parathyroid glands found
Posterior aspect of the thyroid gland
Where does the thyroid gland develop from
Endodermal down growth of the floor of the pharynx
WHt does the thyroid gland grow from and what does it form
Foramen caecum to thyroid cartilage and forms thyroglossal duct
What is the thyroglossal duct
-How are thyroglossal cysts formed
As thyroid gland descends, it forms a small channel called the thyroglossal duct. It usually disappears once thyroid gland reaches its final position in the neck
-When fluid collects in this pocket
What do you need to check for if removing thyroid
Ectopic thyroid tissue
What does the thyroid produce
T3+T4
Calcitonin
What is the type of cell in the thyroid gland
cuboidal epithelium
What is colloid and how does the thyroid deal with this
Thyroid gland stores inactive hormones in the lumen of the follicles. This is activated by the follicular cells on demand which take up the colloid, activate it and pass it to the bloodstream
What are T3 and T4 and which is the active form
T4 is converted to T3 (Active form)
They regulate basal metabolic rate and growth and maturation of nerve
What is the secretion of T3 and T4 regulated by
anterior pituitary
What is the secretion of T3 and T4 regulated by
TSH
What is the role of calcitonin and mechanism of action
Regulates blood calcium level (lowers)
- Inhibits osteoclast reabsorption of bone
- Increases osteoblast activity
What is calcitonin the antagonist for
PTH
What is calcitonin regulated by
Blood Ca2+ levels (independent of pituitary)
What is calcitonin produced by
Parafollicular C cells
What do the 3 veins of the thyroid gland branch off of
Superior vena cava and internal jugular vein
What are the 3 veins of the thyroid gland
Superior, middle and inferior thyroid veins
What are the 2 (or 3) arteries that supply the thyroid gland
Superior and inferior thyroid artery
Some have a third one called thyroidea ima
What is thyroid cancer mainly an adenocarcinoma of
Follicular cells
What is the cause of a goitre
Overactive thyroid
Normally, how many parathyroid glands are there
4
Where do the parathyroid glands come from
third and fourth pharyngeal arches
What do the parathyroid glands secrete and what is this involved in
Parathyroid hormone
-Involved in calcium homeostasis (raises calcium)
How does parathyroid hormone raise serum Ca2+
Increase absorption in gut
Act on kidney to prevent too much loss in urine
Increase osteoclast activity (breakdown of bone) which releases Ca2+ into the blood
What is hyperparathyroidism and what are the cause
Too much calcium in blood because parathyroid glands are too active
- Tumour
- KIdney failure
If you need to remove parathyroid glands, what must you be careful not to damage
Thyroid and recurrent laryngeal nerves
What is the secretory cell of the parathyroid gland
Pale chief cell
