12) Endocrine System Flashcards
What are the major glands of the endocrine system?
- Thyroid gland
- Parathyroid
- Adrenal gland
- Pancreas
- Reproductive glands (Ovaries, Testes)
What is the General Function of Endocrine?
Responsible for synthesis & secretion of hormones that act on specific target organs of tissues
Why is the endocrine system often called a ductless gland?
Because they discharge their
product into interstitial spaces – to be absorbed into the circulatory system
Decribe the gross anatomy of of the thyroid.
- 2 lobes lateral to upper trachea
- Anterior portion of the neck
- Joined in front of the larynx by
the isthmus - Enclosed by fibrous DICT capsule
with septae penetrating the
parenchyma - Function: secretion of T3 & T4
(regulation of the basal metabolic
rate) and calcitonin (calcium
homeostasis) - Stores inactive form of hormone in
follicles
Understanding Thyroid Cells
Follicles are filled with Colloid
Colloid stores the thyroglobulin, which is the inactive form of T3 and T4
cuboidal epithelium surround the colloid and they’re also referred to as follicular cells.
The principal cells produce the glycoprotein component of the thyroidglobulin and convert iodide to iodine
(The principal cells and follicular cells are both in the same area)
Between the principal cells and the follicles, there are cells around it called the parafollicle cells aka C cells. They help with producing calcitonin which which regulates the blood calcium levels
T or F:
The principal cells are the most numerous cell present in
the thyroid.
True
T or F:
The principal cells are NOT responsible for secreting the thyroid hormones as well as thyroglobulin, a glycoprotein.
false
- They are responsible for it
T or F:
In the colloid, the thyroid hormones are stored extracellularly as part of the thyroglobulin which is the main component of the colloid
True
T or F:
The parafollicular cells (C cells) secrete calcitonin, which inhibits osteoclasts from resorbing bone resulting in
decrease in calcium in the blood
* Controlled by the level of calcium in the blood
True
T or F:
The parafollicular cells (C cells) do not have pale / clear cytoplasm, oval nuclei, easy to identify with H&E
F
They are pale and are difficult to identify with H&E
What is the purpose of parafollicular cells decreasing calcium levels?
secrete the hormone calcitonin, which helps reduce blood calcium levels when they are too high
Parafollicular cells and calcitonin reduce blood calcium levels to:
- Prevent the harmful effects of hypercalcemia.
- Maintain a dynamic balance in bone remodeling and calcium homeostasis.
- Complement other regulatory hormones like PTH for smooth physiological functioning.
Where are the parathyroid glands located?
- Parathyroid glands are located attached to the thyroid in the neck to the front of the upper
trachea.
What are the tiny two or three pairs of small pale (coffee-coloured) oval glands embedded in the capsule of the thyroid gland called?
parathyroid glands
- Each gland is about the size of a piece of rice and can be difficult to see macroscopically
The parathyroid hormone (PTH) is very essential to life as the most
important regulator of blood calcium
and phosphorus levels
(regulates serum calcium and
phosphate levels) in partnership with
the thyroid secreting calcitonin)
What do Chief Cells of the Parathyroid Gland do?
Produce and regulate parathyroid hormone (PTH), a hormone crucial for calcium homeostasis.
What does the parathyroid do when the calcium levels are too high or low?
When it’s too high it stop releasing calcium. When it’s too low it starts to release calcium
