Endocrine System Flashcards
Endocrine cells are typically ____
Epithelial cells
Endocrine cells produce secretions called ____
Hormones
What are hormones?
Secretary products of endocrine cells, serve as signaling molecules (effectors) to regulate activities of various cells, tissues, and organs of the body
Hormones act on specific cells with specific ____
Receptor sites
3 chemical classes of hormones
- Steroids
- Small peptides, polypeptides, proteins
- Amino acids, arachidonic acid analogs, inflammatory proteins
3 endocrine distribution control mechanisms
- Endocrine secretion
- Paracrine secretion
- Autocrine secretion
endocrine secretion
*most common
hormones enter blood stream (fenestrated capillaries) and transported to target cells
paracrine secretion
hormones act on adjacent cells or diffuse to nearby target cells
autocrine secretion
hormones act on same endocrine cell
The pituitary gland is attached to the hypothalamus by the ____ and ____
Infundibulum (neural)
Pars tuberalis (vascular)
2 functional components of pituitary gland
Anterior lobe
Posterior lobe
What type of tissue is the anterior lobe of the pituitary gland?
Glandular epithelial tissue
What is Rathke’s pouch?
[anterior lobe] derived from evagination of the ectoderm of the oropharynx toward the brain
components of anterior lobe of pituitary
- pars distalis/anterior
- pars intermedia
- pars tuberalis
what comprises most of the anterior lobe of pituitary?
pars distalis/anterior
pars tuberalis
forms highly vascular sheath around infundibulum which connects to hypothalamus (hypothalamic-hypophyseal portal system)
what type of tissue is the posterior lobe of the pituitary?
neural secretory tissue
posterior lobe of pituitary is derived from…
down growth of neuroectoderm of lower 3rd ventricle of developing brain
components of posterior lobe of pituitary (neurohypophysis)
infundibulum
pars nervosa
infundibulum
contains neurosecretory axons emanating from hypothalamus (hypothalamic-hypophyseal tract)
pars nervosa
contains neurosecretory axons and their endings (arising from hypothalamus)
hypothalamic-hypophyseal tract
axons from hypothalamus carry hormones secreted by neurons from hypothalamus through the infundibulum into the pars nervosa
hypothalamic-hypophyseal portal system
blood vessels carry regulatory peptides from neurons in hypothalamus to cells of anterior pituitary (pars distalis) where they control cell secretion
hormones of adenohypophysis (anterior pituitary/lobe)
tropic and non-tropic hormones
tropic hormones
regulate other endocrine glands (ACTH, TSH, FSH, LH)
non-tropic hormones
directly act on target organs that are not endocrine (GH, PRL)
organization of cells of pars distalis
clumps & cords separated by fenestrated capillaries and supporting reticular CT
3 cell types of pars distalis
- chromophils: basophils, acidophils
- chromophobes
chromophils pick up staining colour due to…
their hormone content
acidophils produce and secrete…
GH - growth hormone (somatotropin)
PRL - prolactin
basophils produce and secrete…
- FSH - follicle stimulating hormone
- LH - luteinizing hormone (ICSH in men, interstitial cell stimulating hormone)
- ACTH - adrenocorticotropic hormone
- TSH - thyroid stimulating hormone
pars intermedia structure
- thin remnant of posterior wall of Rathke’s pouch, borders pars distalis
- surrounds series of colloid filled cysts and/or intraglandular cleft (vestigial cleft) representing residual lumen of Rathke’s pouch
pars nervosa is not…
an endocrine gland
function of pars nervosa
storage site for hypothalamus neurosecretions and release of hormones into fenestrated capillaries (endocrine release)
pars nervosa
hormones accumulate in axonal terminal dilations called ____
Herring bodies (neurosecretory bodies)
Pars nervosa
hormones in Herring bodies
- ADH - antidiuretic hormone/vasopressin
- Oxytocin
what is the predominant cell of the pars nervosa?
pituicytes (resemble astrocytes)
function of vasopressin/ADH
increases water permeability of renal collecting ducts
function of Oxytocin
stimulates contraction of mammary gland myoepithelial cells and uterine smooth muscle
the hypothalamus regulates pituitary gland activity via ____
negative feedback loop
thyroid gland function is essential to…
normal growth and development
what is the structural and functional unit of the thyroid gland?
thyroid follicle
thyroid follicle is formed by…
follicular cells (simple cuboidal epithelium with microvilli)
follicular cells produce…
thyroid hormones: T3 and T4 (thyroxine)
function of T3 and T4
- regulate cell and tissue basal metabolism and heat production
- influence body growth and development
thyroid follicles contain ____
colloid
colloid
gel-like mass containing thyroglobulin
thyroglobulin
inactive precursor form of thyroid hormone
parafollicular cells location
periphery of follicular cells
parafollicular cells produce ____
calcitonin
calcitonin
lowers blood Ca by inhibiting osteoclast activity
epithelial cells of parathyroid
principal cells
oxyphil cells
principal (chief) cells produce ____
PTH - parathyroid hormone
PTH (parathyroid hormone) function
increases blood Ca
3 targets of PTH
- osteoblasts
- kidney
- small intestine
oxyphil cells
function not fully understood, thought to be exhausted principal cells
regions of adrenal glands
cortex & medulla
adrenal cortex secretes ____
steroid hormones
3 zones of adrenal cortex
- zona glomerulosa
- zona fasciculata
- zona reticularis
zona glomerulosa produces ____, such as _____
mineralocorticoids: aldosterone
aldosterone function
major regulator of Na & K balance by increasing kidney absorption of Na and secretion of K
zona fasciculata produces ____, such as ____
glucocorticoids: cortisol
cortisol function
- gluconeogenesis (& glycogenolysis)
- immune & inflammatory reponses
cortisol is regulated by ____
ACTH (anterior pituitary)
zona reticularis produces ____, such as ____
weak androgens: DHEA (dehydroepiandrosterone)
DHEA is converted to ____
testosterone (& estrogen)
what are the cells of the adrenal medulla
parenchymal cells = chromaffin cells
what are chromaffin cells?
specialized secretory cells supported by reticular fibers and many wide-open sinusoidal capillaries
chromaffin cells secrete ____
catecholamines: epinephrine & norepinephrine
function of catecholamines
- regulate stress response
- stimulate glycogen breakdown (elevate blood glucose)
epinephrine is stored in….
small, less electron dense granules
norepinephrine is stored in…
larger, more electron dense granules
epinephrine function
- increase HR
- dilate bronchioles
- dilate arteries of cardiac & skeletal muscle
norepinephrine function
- constrict blood vessels of digestive system & skin
- increase blood flow to heart, muscles, brain
2 main types of parenchymal cells of the pineal gland
- pinealocytes
- interstitial glial cells (neuroglial cells - modified astrocytes)
pinealocytes produce ____
melatonin
melatonin function
(tryptophan derivative)
regulate daily body rhythms and day/night cycle (circadian rhythm)
interstitial glial cell function
unmyelinated tracts of sympathetic fibers associated with photoreceptor neurons in the retina, run into pinealocytes to stimulate melatonin release in periods of darkness
copora arenacea
“brain sand”
- characteristic feature of the pineal gland
- formed by mineralization of extracellular protein deposits
- increases in size & number with age
