Anatomy of the Endocrine System Flashcards
Define an exocrine gland
Exocrine glands have ducts and secrete onto a surface e.g the sebaceous glands of the skin.
Define an endocrine gland
Do not have ducts and secrete hormones directly into the blood stream e.g thyroid
What hormones does the thyroid gland secrete?
Thyroxine (T4)
Triiodothyronine (T3)
Thyrocalcitonin
What do T3 and T4 do?
Increase metabolic activity
What does thyrocalcitonin do?
Lowers the levels of blood calcium
What does the isthmus of the thyroid do?
Connects it’s two lateral lobes
What is the pyramidal lobe?
Remnant of embryological development of the thyroid gland
What cells secrete parathyroid hormone?
Chief cells
Where are the parathyroid glands located?
4 small endocrine glands found on the posterior of the thyroid
What does parathyroid hormone do?
Increases blood calcium levels
How does parathyroid hormone increase blood calcium levels?
- Mobilises bone calcium to increase calcium levels in the blood.
- Stimulates absorption of dietary calcium from the small intestine.
- Stimulates the reabsorption of calcium in the kidney
When does embryological thyroid development begin?
Week 3
Explain the embryological development of the thyroid.
- Endodermal thickening at the back of the tongue
- Thickening leads to a diverticulum
- Diverticulum grows inferiorly into the mesenchyme where it forms the thyroglossal duct.
- Thyroglossal duct elongates and grows becoming bilobed.
- Thyroglossal duct solidifies becoming a solid cord of cells
- Bilobed portions grow to form the thyroid gland
What is a diverticulum?
Outgrowth
What is the remnant of the thyroglossal duct known as?
Pyramidal lobe
What is the foramen cecum?
Site of origin of the thyroid gland, located at the back of the tongue.
How do thyroglossal cysts form?
Thyroglossal duct fails to close properly allowing secretion of mucus down the duct, this forms a cyst which usually needs to be removed surgically.
What proportion of the pancreas has an endocrine function?
5%
Where are the endocrine cells of the pancreas located?
Islets of langerhans
What are the primary hormones secreted by the pancreas?
- Gastrin
- Glucagon
- Insulin
- Somatostatin
- Vasoactive intestinal polypeptide
What does gastrin do?
Stimulates the secretion of gastric acid by parietal cells of the stomach.
What does glucagon do?
Raises blood glucose through gluconeogenesis and glycogenolysis in the liver.
What does insulin do?
Promotes absorption of glucose form the blood into liver, fat and skeletal muscle cells.
What does somatostatin do?
- Inhibitory hormone that suppresses the release of gastrointestinal hormones and pancreatic hormones.
- Reduces smooth muscle contractions and blood flow to the small intestine.
- Suppresses appetite and digestion.
What does VIP do?
- Induces smooth muscle relaxation, and secretion of water in pancreatic juice and bile.
- Potent vasodilator
Where is erythropoetin produced?
JGA in the kidneys
What does EPO cause?
Causes HSC differentiation into RBC’s
What does HSC mean?
Haemopoeitic stem cell
When is EPO used?
In the end stage of kidney failure to treat anaemia.
Performance enhancing drugs - cyclists
What is anaemia?
Lack of iron in the blood leads to a lack of production in the number of RBC’s
What is the RAAS system?
- Renin is produced by the kidneys in response to decreased blood pressure.
- Renin travels to the liver where it converts angiotensinogen into angiotensin 1.
- Angiotensin 1 travels in the blood to the lungs.
- ACE is present in the lungs and converts angiotensin 1 into angiotensin 2.
- Angiotensin 2 causes vasoconstriction and stimulates aldosterone production in the adrenal gland.
What does aldosterone do?
Aldosterone acts on the kidneys causing increased sodium and water retention. This increases blood volume which in turn increase blood pressure.
What does angiotensin 2 do?
- Potent vasoconstrictor
- Acts on g-protein coupled receptors in the kidneys stimulating Na+ reabsorption.
- Stimulates aldosterone production in the adrenal gland.
What is the shape of the right adrenal gland?
Pyramid shaped
What is the shape of the left adrenal gland?
Crescent shaped
What is produced by the cortex of the adrenal gland?
Mineralcorticoids such as aldosterone
Glucocorticoids such as cortisol
Androgens involved in the development of the male sex organs
What are the three regions of the adrenal cortex?
in order
Zona glomerulosa
Zona fasciculata
Zona reticularis
What does the zona glomerulosa release?
Mineral corticoids such as aldosterone
What does the zona fasciculata produce?
Glucocorticoids such as cortisol
What does the zona reticularis produce?
Androgens such as DHEA
What is produced by the adrenal medulla?
The catecholamines Epinephrine and Norepinephrine
What is the blood supply to the pituitary gland?
Superior and inferior hypophyseal arteries (branches of the internal carotid)
Hypophyseal veins
Where do the hypophyseal veins of the pituitary gland drain into?
Cavernous sinuses
How does communication from the hypothalamus to the anterior and posterior pituitary differ?
Anterior pituitary sends hormones in the nervous system directly to the anterior pituitary in the blood stream.
Posterior pituitary - receives inhibitory or stimulatory impulses from nerve cells in the hypothalamus.
What does the pineal gland do?
Secrete melatonin and establish circadian rhythms
