Final - Endocrine Flashcards
Cell surface receptors.
interact with peptide hormone of catecholamine; generate 2nd messenger that amplifies signal and alters target cell
Intracellular receptors.
steroid and thyroid (lipidy) hormones penetrate plasma and nuclear membranes to make large complexes and bind chromosomal DNA to alter transcription (lipid ligand can cross plasma membrane and bind in cytoplasm, then the structure goes into DNA and binds there)
What are the two ways “substances” are sent from hypothalamus to the pituitary gland?
- bloodstream - anterior receives via hypophyseal portal veins - true endocrine
- nerve endings - posterior receives
Explain what substances are sent via which method to the pituitary.
- cell surface: peptides or catecholamines
- intracellular: steroids and lipidy hormones
What does the pituitary gland do upon receiving substances from the hypothalamus?
pituitary sends its own hormones out to target organs, which stimulates them to release their hormones/secretions
List the target organs of the hypothalamus-pituitary axis (7).
- gonads
- adrenal cortex
- thyroid
- mammary gland
- liver
- kidney
- mammary gland
Explain the difference b/w pars nervosa and pars distalis with staining.
- pars nervosa: stains lighter (increase in myelin and nervous tissue)
- pars distalis: stains darker
What histological features are located in the parts of the hypophysis?
- pars intermedia: cysts, basophils, chromophobes
- parts distalis: basophil, acidophil, chromphobes
- pars tuberalis: highly vascular
- all have epithelial cords and clusters
What histological features are located in the pars nervosa?
axons, pituicytes, herring bodies
Are herring bodies cells?
no, they are ends of axons from hypothalamus - release neuropeptides - oxytocin and vasopressin
How do acidophils, basophils, and chromophobes appear?
acidophils: bright purple with red
basophils: dark purple
chromphobes: cytoplasm almost non-colored
How does the pineal gland know whether to secrete melatonin?
- photosensitive organ
- light stops the production of melanin
- when its dark the suprachiasmatic nucleus become uninhibited and pineal gland produces melanin
What is the effect downstream of the pineal gland secreting melatonin?
melatonin inhibits neurosecretory neurons of the hypothalamus that make GNRH which leads to a decrease in gonadal steroids (decrease in FSH & LH)
Histological features of the pineal gland.
- capsule (think and continuous with pia mater)
- parenchyma (CT trabeculae and cords of cells, 2 cell types pinealocytes and interstitial cells)
- brain sand (calcified secretions from pinealocytes - CAPO4 - increases in age)
Describe the histology of the thyroid gland.
functional units = secretory follicles
- follicle epithelium- simple cuboidal (some columnar)
- colloid - gel-like mass of thyroglobulin (T3, T4)
- parafollicular cells in basal lamina
What is secreted from the thyroid?
- follicular cells: T3 & T4
- parafollicular cells: make calcitonin (decrease blood calcium)
What are the effects of the secretions of the thyroid (4)?
- In target organs
1. increase growth
2. increase development
3. increase metabolism
4. increase heat production
Describe the histology of the parathyroid gland.
vascularized epitheloid - more CT & adipose with age
What is secreted by the parathyroid gland?
- principal (chief) cells: secretes PTH (increase blood calcium and phosphorous)
- oxyphils: unknown - maybe store high energy macromolecules
Do we know the function of every cell in the parathyroid?
no, oxyphils unknown just know they don’t secrete
What are the effects of secretions of the parathyroid?
- increase blood calcium and phosphorous
1. reabsorb from bone
2. decrease kidney excretion of calcium
3. increase urine PO4 excretion
4. regulate hydroxylation of D3
5. increase intestine absorption of Ca
Describe histology of the adrenal gland.
CT that extends into parenchyma as trabeculae.
What are the secretions of each zone of the adrenal cortex and adrenal medulla?
- zona glomerulosa: aldosterone
- zona fasciculata: glucocorticoids (i.e. cortisol)
- zona reticularis: gonadocorticoids (i.e. DHEA or weak androgen)
- medulla: catecholamines (Epi, NER)
What are the downstream effects of the secretions of the adrenal cortex and adrenal medulla?
- aldosterone: RAAS pathway (increase bp)
- cortisol: lipid metabolism (pos. correlation with lipid storage) & blood sugar
- weak androgens
- fight or flight
Explain the specialization of the chromaffin cells in the adrenal medulla.
sympathetic fibers send ACH to chromaffin cells which send E/NER through fenestrated capillaries (endocrine here)
- differs from basic endocrine secretion of cortex
- chromaffin: modified neurons
Does the hypothalamus continually secrete the hormones that it makes?
No, the hormones secreted by the target organs bind back to the hypothalamus and inhibit production
Ex. hypothalamus -> (TRH) -> adenohypophysis -> (TSH) -> thyroid -> (T3, T4) -> target organs -> inhibit of TRH at hypothalamus
