The thyroid and parathyroid glands Flashcards
Where is the thyroid gland?
Anterior to the trachea and inferior to the larynx
What vertebral level and anatomical locations help find the thyroid gland?
It is located between the vertebral level of C 5- T 1 and between the cricoid cartilage
cartilage and the 6th tracheal ring.
What does the isthmus lie opposite?
1st to 2nd tracheal rings
What strap muscles overlie the thyroid gland?
Sternohyoid muscle
Sternothyroid muscle
Name the two nerves that supply the muscles of the vocal cords and describe their location in relation to the thyroid gland:
- Recurrent laryngeal nerve**. – runs between trachea and oesophagus
- Superior laryngeal nerve- Branch of vagus nerve at the level of C2 vertebra and descends medially towards the thyrohyoid membrane, the membrane between the thyroid cartilage and hyoid bone
From which major artery in the neck does the superior thyroid artery arise?
External carotid artery
From which artery does the inferior thyroid artery arise?
Thyrocervical trunk which is a branch of the subclavian artery
Into which vein does the superior thyroid vein drain?
IJV
Into which vein does the middle thyroid vein drain?
IJV
Into which vein does the inferior thyroid vein drain?
Brachiocephalic vein
Where are the hormones of the thyroid gland stored?
in cavities, surrounded by secretory cells. These make up a follicle. Within the cavity of the follicle, the hormone is bound to a glycoprotein and is called as colloid
What happens during secretion to the thyroid hormone?
During secretion the hormone is re-absorbed from the cavity, and then released into the surrounding interstitial spaces.
How can you recognise thyroid glands?
easy histology as pinkish circles looking like this. Every single colloid follicle is lined by a simple non-stratified relatively simple type of epithelium. Can see plexus of blood vessels between the little follicle circles.
What do follicular cells look like?
are almost columnar in appearance in some regions, whilst elsewhere they have a low cuboidal appearance
What does thryoid hormone make?
a hormone called calcitonin and these are found in spaces between the cells.
What do parafollicular cells look like?
Have a red cytoplasm
1 = Colloid follicle
2 = Interfollicular connective tissue (Toby thinks follicular cells so gonna be brought up tomorrow
3 = Parafillicularcells
What type of cell do you see lining the follicle?
Squamous follicular cells
What colour does the colloid stain?
Yellow
What do the C cells secrete?
Calcitonin
What hormones does the thyroid gland secrete?
Thyroxine
Triiodothyronine
Where does the parathyroid glands lie?
Lateral half of the posterior surface of each thyroid lobe external to the thyroid fibrous capsule
How many parathyroid gland most people have?
4
They are seperated from the thyroid gland by a thin fibrous capsule
The superior parathyroids are situated at?
the level of the inferior border of the cricoid cartilage
. The inferior parathyroids are usually located where?
near the inferior poles of the thyroid, though their position is variable.
Arterial supply to both superior and inferior parathyroids is predominantly from what?
the inferior thyroid arteries
What is venous drainage done by?
via the veins draining the thyroid to the internal jugular veins.
What is this?
Parathyroid gland
The parathyroid – chief cells (1) and oxyphil cells (2). Chief cells are more numerous and have a darker staining cytoplasm. Lighter cells are oxyphil cells. The white parts are fat.
What hormone is secreted by the parathyroid gland and what is the action of this hormone?
Parathyroid hormone- Maintains appropriate balance of calcium in blood stream and tissues
What cells does this hormone act upon and what is their subsequent action?
Stimulates the conversion of immature osteoclasts to mature type- Subsequently increasing bone degradation
