10/7 Edocrine gland histology Flashcards
what are the plus/minus of synaptic signaling?
fast, local, signal reception and termination is to guaranteed geography;
expensive energetically to set up and maintain
what are the plus/minus of the endocrine signaling
Cheap energetically, geography is widespread
slow, signal reception and termination is not guaranteed,
What is endocrine feedback
links signal production to response and hopefully regulates the response.
what type of feedback is it when the product generated inhibits the signal generating the product?
negative feedback
what is a famous example of positive feedback?
hypothalamus/pituitary release of LH to ovary which releases estradiol, which stimulates release of LH
what is the difference in signal and product feedback
product feedback is from the product to higher up in the chain to a cell that didn’t produce the signal. signal feedback is to the same cell that excreted the signal.
why would you want some signal feedback
to give immediate and direct feedback to the producing cell, and lead to tighter control.
why would complex systems be used in the body
they see to be more stable, where a chain of signals give rise to a product where each step has product and signal feedback
general features of endocrine glands
ductless
specificity conferred by receptors on target cells
predominantly parenchyma ;little stroma
abundant blood supply, glands often contain fenestrated capillaries
typically, each cell is adjacent to capillary or lymph vessels
features of protein and polypeptide hormones
hydrophilic synthesized on RER stored in granules bind to receptors on cell membrane activate second messenger systems
properteis of steroid derivatives
hydrophobic synthesized on SER, not stored diffuse through cell membrane bind to cytoplasmic receptors act as transcription factors
properties of the tyrosine and phenylalanine derivatives (mixed)
mixed hydrophobic/philic
thyroxien is hydrophobic and binds to cytoplasmic receptors, acts as a transcription factor
epinephrine adrenalin binds to G-protein coupled cell surface receptors.
exmp. of protein and polypeptide homones
insulin, glucagon
exmp. of steroid derivitive hormones
progesterone, estradiol, testosterone, cortisol
what is the gland that links the endocrine and nervous systems
the pituitary or the hypophysis (same thing)
where is the pituitary?
in the base of the brain!
describe the structure of the pituitary
hypothalamus, connected by the stalk and portal vessels to the anterior pituitary with the posterior pituitary behind that.
anterior pituitary other name
pars distalis or the adenohypophysis or pars anterior
posterior pituitary other name
pars nervosa or the neurohypophysis
what is the feedback molecule for adrenal back to the pituitary?
cortisol is the feedback to the pituitary!
what is the difference in synaptic and endocrine signaling
synapis: use a junction with close or direct contact with ion channels (neurons) etc. used by the nervous and immune system. used for behavior control
Endocrine is diffuse secretion with G-protein coupled, enzyme coupled, intracellular receptors, used by pretty much everything used for homeostatsis control
the stalk between the hypothalmus and anterior pituitary
Pars tuberalis that surrounds infundibulum
what does the pars tuberalis secrete
secretes primarily gonadotropins
filled with basophilic cells; colloid in the pituitary
pars intermedia (between the anterior and posterior piuitary)
what are the three hormone producing places in the hypothalamo-hypophyseal system
- Neurons in hypothalamic nuclei secrete releasing and inhibiting factors into the primary capillary plesxus in the median eminance – influence the release form the pars distalis (anterior)
- Neurons in the suprcoptic and paraventricular nuclei of hypothalamus make antidiuretic hormone (ADH) and oxytocin stored in and released form the neurophypophysis (posterior)
- cells in the anterior Pituitary (pars distalis) secrete six important hormones into the secondary capilary plexus: hGH (human growth hormone); ACTH (adrenocorticotropic hormone); TSH: Thyroid stimulating Hormone; LH (luteinizing hormone); FSH (follicle stimulating hormone);
describe the portal system of the hypothalamo-hypophyseal:
primary capillary, and Portal system in the stalk; portal veins to the anterior pituitary; secondary capilaries in the pituitary.
what are the cell types of the pars distalis
3 types in normal H/E stain:
- Basophils (dark purple)
- acidophils (dark redish)
- chromophobes (inbetween color)
what is secreted by basophils of the pars distalis
ACTH; TSH; FSH; LH
what does ACTH doe
Act on the adrenal cortex to cause secretion
what does TSH do?
act on the thyroid to cause secretion
what does the LH and FSH do?
act on the testies and ovaries
what is secreted by the acidophils
Growth hormones; prolactin
what does prolactin do?
mamilary gland and milk production
how is the control of release of hormones in the posterior and anterior pituitary differ?
the anterior relies on signals through the portal system of vessels. the posterior is from axon and nerve impulse control.
what hormones are secreted by the neurohypophysis?
- -ADH (antidiuretic and known as vasopressin)
- -oxytocin (synthesized by neurons in SO and PV nuclei, uterus and mamillary gland contraction)
what is between the neurohypophysis and the pars distalis histologically?
rathke’s pouch remnant;
pars intermedia
how do the histological views of neurohypophyisis and the pars distalis differ?
the neurohypophysis is all boring and neuronal looking and the pars distalis is colorful and basophilic and acidophilic etc.
what is is the pars intermedia?
axons and glia – parenchyma of unmyelinated axons and stroma of glial cells
benign tumors of the pituitary gland
pituitary adenomas
what if a big adenoma of the pituitary
hypersecretion especially of prolactin that causes milk and irregular cycles in women and ED and no libido in men
– or just compress stuff and cause headache and peripheral vision loss
histological appearence of the adrenal gland
dense connective tissue on the outside, very little other connective tissue, septa (lines through the cells) bring nerves and blood supply; very vascularized!
parenchymal cells derived form neural crest cells
chromaffin cells of the adrenal medulla
how is the adrenal medulla innervated?
from sympathetic preganglionic nerves
what are catecholamines
epinephrine and norepinephrine
3 zones of the adrenal cortex
Z. glomerulosa
Z. fasciculata
Z. reticularis
what is the histology of Z. GLomerulosa
cells in whirls or ovoid clusters (circles?)
what mineralocorticoid would be loss if the Z. glomerulosa was gone?
aldosterone
what must be present to secrete aldosterone?
ACTH, but regulated by angiotensin II and K+ in extracellular fluid
what would happen to the pee if no aldosterone?
much more sodium
Aldosterone stimulates resorption of sodium by collecting tubules and ducts
Histology of Z. fasciculatat
Looser, lighter staining cells then the zone above or below, arranged in almost linear elements
what would we not secrete if lost the zona fasciculata
cortisol, corticosterone
what does the product secreted by Z. fasciculata do?
glucocorticoids stimulate synthesis of glucose in liver, promote breakdown of fat and protein; anti-inflammator; and resist stress.
What is the histology of Z. reticularis?
cells in anastimosing cords, darker red and staining then the area above
what is secreted by the Z. reticularis?
DHEA (weak androgen)
HPA axis
glucocorticoids (cortisol) give neg. feedback to the hypothalamus and Anterior Pituitary to down reg. ACTH production.
–hypothalamus- pituitary - adrenal axis —
