Endocrine system Flashcards
(30 cards)
Endocrine gland functions?
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?
POSITIVE FEEDBACK LOOP on uterine smooth muscle during labor (will stimulate uterine contractions, and uterine contractions stimulate oxytocin release)
Contracts myoepithelial cells of mammary alveoli for milk letdown; which can be stimulated by suckling or by psychological factors (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- somatotropes(GH; via growth hormone releasing hormone), and prolactin- mammotropes (PRL). These have direct effect on end-organs rather than on other endocrine organs.
What does growth hormone do?
-Increases synthesis of growth factors
-Increases cell division, protein synthesis, lipolysis
-Regulates blood sugar:
low blood sugar-> GRH-> GH-> glycogen breakdown
High sugar–> Somatostatin-> Decreased GH- 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? Where are they most prominent?
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 parathyroid 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 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.
