18.7 Thyroid Gland Flashcards
(22 cards)
Thyroid gland
Located inferior to larynx, composed of right and left lateral lobes, with a third small pyramidal lobe. Are all connected by the isthmus (passage).
Thyroid follicles
Microscopic spherical sacs in the thyroid gland.
Follicular cells
Compose wall of follicle
Thyroid hormones
T3 and T4
Parafollicular cells (C Cells)
Produce calcitonin- aids in calcium homeostasis
8 functions of thyroid hormones:
1) increase basal metabolic rate
2) synthesis of Na+/K+ ATPase
3) increase body temp
4) stimulate protein synthesis
5) increase use of glucose and fatty acids for ATP production
6) stimulate lipolysis
7) enhance some actions of catecholamines
8) regulate development and growth of nervous tissue and bones
Steps for Synthesis and secretion of thyroid hormone t3&t4
1) iodide trapping
2) synthesis of thyroglobulin
3) oxidation of iodide
4) iodination of tyrosine
5) coupling of T1 & T2
6) pinocytosis and digestion of colloid
7) secretion of thyroid hormones
8) transport in the blood
Parathyroid hormone
Increases # of osteoclasts. Major regulator of levels of calcium, magnesium, and phosphate ions.
4 types of parathyroid glands that make up thyroid glands
Left superior
Right superior
Left inferior
Right inferior
Adrenal cortex
Produces steroid hormones for the body
Outer layer of adrenal gland
3 zones of adrenal cortex
Zona glomerulosa -outer zone- “cells arranged in spheres “
Zona fasciculata- middle zone- “cells arranged in little bundles”
Zona reticularis - inner zone- “cells arranged in branches”
Aldosterone
Major hormone secreted by outer zone of adrenal cortex. Regulates sodium and potassium ions.
Angiotensinogen
A plasma protein produced by the liver
Renin
An enzyme that converts angiotensinogen into
“angiotensin I”
2 ways angiotensin II increases blood pressure
1) acts to constrict blood vessels by causing contraction of smooth muscle
2) stimulates secretion of aldosterone
Glucocorticoids
Regulate metabolism and resistance to stress
6 effects of glucocorticoids
1) protein breakdown
2) glucose formation
3) lipolysis
4) resistance to stress
5) anti inflammatory effects
6) depression of immune responses
Negative feedback loop for glucocorticoid secretion
1) Stimulus
2) Controlled condition- glucocorticoid condition in blood
3) receptors- neurosecretory cells in hypothalamus
4) control center- corticotrophs in anterior pituitary
5) effectors- cells of zona fasciculata in adrenal cortex
6) response- increased glucocorticoid level in blood
All is back to normal…:)
Androgens (DHEA mainly)
An androgen found in both sexes, insignificant in comparison to testosterone in men, but significant in woman.
Promotes sexual drive in women. Is the only source of estrogen in women.
Adrenal medulla
Inner region of adrenal gland. Modified sympathetic ganglion of the ANS. The cells secrete hormones
Chromaffin cells
Hormone producing cell
Epinephrine and norepinephrine
Increase blood flow to the heart, liver, skeletal muscles and adipose tissue.
