Endocrine - Part 1 Flashcards
what glands/cells compose the endocrine system?
- pituitary (adenohypophysis)
- adrenal (suprarenal) glands
- thyroid
- parathyroids
- pineal gland
- islets of langerhans
- DNES (enteroendocrine cells of intestine, heart, kidney)
where is the pituitary gland attached?
attached to hypothalamus by infundibulum
what is the glandular portion of the pituitary called and where does it come from?
adenohypophysis - from ectoderm of primitive oral cavity
what is the neural portion of the pituitary called and where does it come from?
neurohypophysis - from neuroectoderm
divisions of the adenohypophysis
- pars distalis
- pars tuberalis
- pars intermedia
divisions of neurohypophysis
- pars nervosa
- infundibulum
what makes up the anterior lobe of pituitary?
pars distalis + pars tuberalis
what makes up posterior lobe of pituitary?
pars nervosa + pars intermedia
describe control of secretion by adenohypophysis
hypothalamic nuclei -> peptide hormones into primary capillary plexus of infundibulum -> stimulate and inhibit release of hormones by anterior pituitary
what stimulatory hormones are released by the adenohypophysis?
for:
- thyrotropin
- gonadotropin
- somatostatin
- growth hormone
- corticotropin
what inhibitory hormone is released by the adenohypophysis?
to inhibit prolactin release
what two arteries supply the hypophysis?
superior and inferior hypophyseal arteries
what do the inferior hypophyseal arteries primarily supply?
pars nervosa
what do the superior hypophyseal arteries supply?
- median eminence
- upper infundibulum
- lower infundibulum via connection to inferior hypophyseal arteries
describe ends of arteries supplying median eminence and infundibulum?
end in capillary plexuses
what drains areas hypophyseal areas supplied by plexuses?
hypophyseal portal veins
composition of pars distalis (overall + 7 cell types)
secretory cells w/i CT stroma w/ fenestrated capillaries:
- chromophobes
- undifferentiated nonsecretory cells
- degranulated chromophils w/ few granules
- CT/follicular cells
- chromophiles
describe pars distalis chromophobes
- stain poorly: look white/clear
- 3 subpopulations = about 50% of cells
describe pars distalis follicular cells
- form a stromal network to support chromophil cells
- may have phagocytic fxn
pars distalis chromophiles: acidophilic vs. basophilic
acid: stain w/ eosin and orange-G, NOT w/ PAS
baso: stain w/ hematoxylin, basic dyes
pars distalis acidophils: secretion
peptide hormones
pars distalis acidophils: size compared to basophils
smaller than basophils, more granules
pars distalis acidophils: somatotroph secretions
GH, somatotropin (growth hormone)
pars distalis acidophils: control of somatotrophs
- GH-releasing factor
- GH-inhibiting factor (somatostatin)
pars distalis acidophils: mammotroph secretions
- prolactin (to stimulate and maintain lactation)
- numbers increase during lactation
pars distalis acidophils: control of mammotrophs
- thyrotropin-releasing factor (TRF)
- prolactin-inhibiting factor (dopamine)
pars distalis basophils: secretion
glycoprotein hormones (PAS+)
pars distalis basophils: gonadotroph secretions
- FSH
2. LH
function of FSH
- stimulates development of ovarian follicles
- acts on Sertoli cells to stimulate production of ABP
function of LH
- stimulates steroidogenesis in ovarian follicles and corpus luteum
- controls rate of testosterone synthesis by Leydig cells
pars distalis basophils: corticotroph secretions
ACTH (adrenocorticotropin)
function of ACTH
stimulate growth and steroid synthesis in zone fasciculata (sugar) and zone reticularis (sex) in adrenals
pars distalis basophils: thyrotroph secretions
thyrotropin/TSH (approx 5% of cells)
pars distalis basophils: control of thyrotrophs
TRF (thyrotropin-releasing factor)
pars distalis: what can H&E distinguish?
only acidophils, basophils, chromophobes
pars nervosa: composition
- non-myelinated axonal processes
- pituicytes
pars nervosa: where are cell bodies of non-myelinated axonal processes?
paraventricular and supraoptic nuclei of hypothalamus
pars nervosa: what are pituicytes?
- astrocyte-like glial cells
- contain glial fibrillary acidic proteins
- often contain pigment granules
pars nervosa: where do neurons end?
in close proximity to fenestrated capillary network
pars nervosa: what do axons contain?
neurosecretory granules - large granule-filled dilations near axon terminals = Herring bodies
pars nervosa: what do the hypothalamic neurons release near capillary plexus?
- oxytocin
- antidiuretic hormone (vasopressin)
what produces oxytocin, primarily and secondarily?
pri: paraventricular nucleus cells
sec: supraoptic nucleus cells
purpose of oxytocin?
- mammary glands: stimulates milk ejection
- uterus: smooth muscle contractions for childbirth
what produces antidiuretic hormone, primarily and secondarily?
pri: supraoptic nucleus cells
sec: paraventricular nucleus cells
purpose of antidiuretic hormone?
stimulates water reabsorption by renal medullary collecting ducts
pars nervosa: what is neurophysin?
binding/carrier protein - complexes with neurohypophyseal hormones for transport down axons
pars intermedia: size in humans?
very small
pars intermedia: contents
- basophils
- chromophobes
- Rathke’s cysts
pars intermedia: what are Rathke’s cysts and what are they lined by?
- cuboidal epithelium lined cavities
- remnants of Rathke’s pouch
pars tuberalis: describe contents
- veins of phyphyseal portal system (highly vascular)
- mostly gonadotropes
what does excess growth hormone cause?
acromegaly
what can prolactin secreting tumors cause?
infertility - lack of ovulation
what is the most common cause of hypopituitarism in adults?
pituitary tumors (adenomas)
describe intrinsic pituitary destruction
(primary pituitary destruction) - hormone-secreting cells of ant pit are destroyed
-can involve some or all hormones
results of poor anterior lobe function (4 things)
- failure of lactation
- amenorrhea
- poor thyroid function
- adrenal insufficiency
results of poor posterior lobe function (1 thing)
diabetes insipidus = impairment of water resorption in distal renal tubuli:
- polyuria
- polydipsia
