CTO Quiz #5 Flashcards
What are the functions of the endocrine system?
The functions include: regulation of growth, reproduction, metabolism, fluid levels, glandular secretion etc.
How does the hypothalamus affect the endocrine system?
The hypothalamus is the site of release of the releasing and inhibiting factors that enter the hypothalamo-hypophyseal portal system and affect anterior pituitary function. It is also the site of neurons that manufacture oxytocin (paraventricular nucleus) and vasopressin (supraoptic nucleus) that send axons through the hypothalmo-hypophyseal tract to end in the posterior pituitary gland. These hormones are released into the blood stream, although they are not made in the posterior pituitary.
What is the “master gland of the body”?
The pituitary gland controls many other endocrine glands.
What are the functions of oxytocin?
Oxytocin acts on uterine smooth muscle during labor as part of a positive feedback loop. It also contracts myoepithelial cells of mammary alveoli for milk letdown. This may be stimulated by suckling or by psychological factors such as a baby crying.
What is the function of antidiuretic hormone?
ADH promotes water resorption from the collecting tubules & vasoconstriction
What is the embyologic origin of the adenohypophysis?
The adeohypophysis (anterior pituitary) derives from Rathke’s Pouch
What is the capillary organization of the anterior pituitary?
Many capillaries are part of the hypothalamo-hypophyseal portal system that takes releasing factors from the median eminence of the hypothalamus to the anterior pituitary. This system has many fenestrated capillaries and no barrier (such as the blood-brain barrier) in the hypothalamus or the anterior pituitary.
What do acidophils of the adenohypophysis secrete?
Acidophils secrete growth hormone (GH; via growth hormone releasing hormone), and prolactin (PRL). These have direct effect on end-organs rather than on other endocrine organs.
What does growth hormone do?
Growth Hormone (GH) is produced by somatotropes under the influence of growth hormone releasing hormone (GRH). It increases the synthesis of growth factors, increasing cell division, protein synthesis, and lipolysis. It also helps regulate blood sugar. Low sugar results in increase GRH, which increases GH, which results in glycogen breakdown. High blood sugar results in increased somatostatin release (growth hormone inhibiting factor), which decreases GH and results in less sugar breakdown.
What does prolactin do?
Prolactin (PRL) promotes milk production. It is produced by lactotrophs and is normally inhibited by the hypothalamus via dopamine release into the hypothalamo-hypophyseal portal system. Suckling reduces this inhibition.
What do basophils of the adenohypophysis do?
Basophils secrete ACTH (corticotropes), TSH (thyrotropes), and FSH, LH (gonadotropes).
What do chromophobes of the adenohypophysis do?
Chromophobes are probably not active in secreting hormones. They may be resting or replacement cells.
What does the thyroid gland control?
The thyroid gland controls metabolism, heat regulation, growth and nervous development.
Describe the histologic appearance of the thyroid.
The thyroid is characterized by large follicles lined by cuboidal follicular cells. There is colloid within the follicles (more in inactive glands) and there are parafollicular “C” cells between the follicles. As with all endocrine glands, there are many capillaries.
What is colloid?
Colloid made of the protein thyroglobulin. This is secreted into follicle by the follicular cells. These cells take up iodine and pump it into the follicle where it iodinates thyroglobulin to make T3 and T4.
How is thyroid hormone secreted?
Under the influence of TSH, follicular cells reuptake thyroglobulin and liberate T3 & T4. This is secreted into the blood stream.
What is the significance of resorption lacunae?
Resorption lacunae are the regions near the active follicular cells where processes of these cells have internalized thyroglobulin, leaving an empty-appearing region adjacent to the cell. These are more prominent in an active thryroid.
What do parafollicular (C) cells do?
C cells make calcitonin, which decreases Calcium in blood by several mechanisms, including decreasing intestinal absorption and renal tubular resorption of calcium and by inhibiting osteoclasts in the bone.
Why is calcium regulation important?
Hypocalcemia results in muscle cramps and muscle tetany. Hypercalcemia results in muscle weakness and can produce confusion and stupor.
Where are the parathyroid glands?
There are usually 4 of them on the back of the thyroid gland. However, the location is variable.
What kind of cells are in the parayroid glands?
Chief cells secrete PTH (parathyroid hormone). Oxyphil cells are more eosinophilic, partially due to lots of mitochondria. These cells have no known function.
What does parathyroid hormone do?
PTH increases Calcium in the blood. It does this by stimulating osteoclasts to break down bone. It also increases calcium resorption from the GI tract by activating vitamin D and incrases calcium resorption from the renal tubules.
What are the layers of the adrenal cortex?
The layers of the adrenal cortex (from superficial to deep) are the zona glomerulosa, the zona fasciculate and the zona reticularis.
What does the zona glomerulosa do?
The zona glomerulosa cells secrete mineralocorticoids (aldosterone), which helps regulate electrolyte and water levels. The hormone is under the influence of the renin-angiotensin system.
What does the zona fasciculata do?
The zona fasiculata cells secrete glucocorticoids (cortisol). This is a hormone that helps the body deal with stressful situations. It increases blood sugar, fat, amino acids, and blood pressure. It has a circadian rhythm, being high in the morning. This is regulated by ACTH from the adenohypophysis.
What does the zona reticularis do?
The zona reticularis secretes androgens. It has little effect in males, but is responsible for testosterone in women and makes estrogen in postmenopausal women.
Where does the adrenal medulla arise from?
The adrenal medulla arises from neural crest cells, in a similar manner to sympathetic ganglion cells.
What are the cells of the adrenal medulla called and what do they do?
The cells of the adrenal medulla are called chromaffin cells. They are innervated by sympathetics preganglionic neurons and secrete epinephrine and some norepinephrine. These hormones will increase blood pressure, heart rate and blood glucose.
What is the endocrine portion of the pancreas called?
The endocrine portion of the pancreas is called the pancreatic islets of Langerhans.
What types of cells are in the endocrine pancreas and what do they do?
Beta cells secrete insulin in response to high blood sugar, which is responsible for getting glucose into cells, thereby lowering blood sugar. Alpha cells secrete glucagon in response to low blood sugar. This hormone causes the liver to break down glycogen into glucose and deliver it to the blood. Delta cells secrete somatostatin, which inhibits local hormone production (insulin and glucagon). F cells produce pancreatic polypeptide (which helps regulate other hormone release).
What are the cells of the pineal gland called and what are the distinctive histologic features?
The functional cells of the pineal gland are pinealocytes. Corpora arenacea (mineral deposits that show up on CT/MRI) are the most distinctive feature.
What does the pineal gland do?
This gland produces melatonin (important in the circadian clock).
What kind of epithelium lines most of the oral cavity?
The oral cavity is lined by stratified non-keratinized squamous epithelium
What is the histologic structure of the tongue?
It is mostly skeletal muscle lined by stratified squamous nonkeratinized epithelium. There are connective tissue bands and minor salivary glands between bundles of skeletal muscle. The posterior 1/3 of the tongue has lymphoid tissue (lingual tonsil) under the stratified squamous epithelium.
What kinds of papillae are on the tongue and what are their structures?
Filiform papillae are the most numerous and appear as short bristles. Fungifom papillae are broader and often have taste buds on their sides. Circumvallate papillae form a row just anterior to the sulcus terminalis and contain a large number of taste buds.
What divides the anterior 2/3 of the tongue from the posterior 1/3
The sulcus terminalis.
