Unit 4 Endocrine Flashcards
divisions of adenohypophysis
pars distalis
pars intermedia
pars tuberalis
neurohypophysis
pars nervosa
infundibulum
origins of adenohypophysis
Rathke’s pouch
oral ectoderm
loses attachment with oral cavity
organs of neurohypophysis
neuroectoderm
outgrowth from floor of diencephalon
remains attached to brain via infundibulum
major cell types
adenohypophysis
chromophobes
chromophils
chromophils
acidophils
basophils
acidophils
somatotropes
mammotropes
somatotropes
secrete somatotropin (hGH); affects epiphyseal plate of long bones
mammotropes
secrete prolactin; stimulates milk secretion
basophils
thyrotropes
gonadotropes
corticotropes
thyrotropes
secrete TSH; causes secretion of thyroid hormones
gonadotropes
- secrete FSH – in females stimulates development of ovarian follicles; in males stimulates Sertoli cells to secrete androgen-binding protein
- secrete LH – in females promotes maturation of follicle and ovulation and maintains corpus luteum; in males called interstitial cell secreting hormone (ICSH) promotes secretion of testosterone by Leydig cells
corticotropes
secrete ACTH; promotes growth of adrenal cortex and secretion of glucocorticoids and gonadocorticoids
hypothalamohypophyseal tract
axons of neurons of supraoptic and paraventricular nuclei
herring bodies
pituicytes
neurohypophyseal hormones
oxytocin
vasopressin (ADH)
oxytocin
made in paraventricular nucleus of the hypothalamus; stimulates smooth muscle of uterus and myoepithelial cells of mammary gland
vasopressin
made in supraoptic nucleus of the hypothalamus; acts on distal tubules and collecting tubules of kidney making them more permeable to water; generates hypertonic urine
pituicytes
glial-like cells
pituitary blood supply
inferior hypophyseal arteries to neurohypophysis
hypothalamohypophyseal portal system
hypothalamohypophyseal portal system
- delivers hypothalamic regulating hormones to adenohypophysis
- superior hypophyseal arteries, primary capillary plexus around stalk and median eminence of hypothalamus
- secondary capillary plexus in adenohypophysis
thyroid gland structure
two lobes
isthmus
connective tissue capsule
thyroid follicles
- follicular cells – simple cuboidal epithelium
- colloid – precursor to thyroid hormones, thyroxine (T4) and triiodothyronine (T3)
thyroglobulin - only endocrine gland to store its secretions; storage is extracellular
- regulated by TSH
parafollicular cells
- produce calcitonin
2. regulated by blood calcium levels
thyroid hormones
- follicular hormones thyroxine and triiodothyronine stimulate metabolic rate
- calcitonin – lowers blood calcium levels by inhibiting bone resorption
parathyroid gland structure
- two pair
- embedded on posterior of thyroid gland
- cords of cells: chief cells, oxyphil cells
parathyroid function
- increases blood level of calcium by increasing number and activity of osteoclasts
- decreases blood level of phosphate by decreasing resorption in kidney tubules, promoting its excretion
adrenal origins
cortex - mesoderm
medulla - neural crest
adrenal cortex zones
zona glomerulosa
zona fasciculata
zona reticularis
zona glomerulosa
- secretes mineralocorticoids – aldosterone
- maintains electrolyte and water balance
- regulated by renin-angiotensin system
- unaffected by ACTH
zone fasciculata
- secrete glucocorticoids – cortisol
- prepares body for maximal immediate energy demands; part of “fight or flight” stress response
- depresses immune function and inflammatory response
- regulated by ACTH
zona reticularis
- secretes gonadocorticoids – dehydroepiandrosterone (DHEA)
- negligible amount compared with testis
- regulated by ACTH
adrenal medulla
- modified sympathetic ganglion
- chromaffin cells – modified post-ganglionic neurons
- secretes epinephrine (80%) and norepinephrine (20%)
- regulated by preganglionic sympathetic neurons
adrenal blood supply
- capsular arteries
- medullary arteries
- cortical capillaries
medullary arteries
- travel through cortex to medulla
2. arterial blood delivered to medullary sinusoidal capillaries
cortical capillaries
- cortical sinusoidal capillaries
2. drain into medullary capillaries
dual blood supply medulla
- arterial blood
- venous blood from cortex
- portal system
- allows glucocorticoids from cortex to convert norepinephrine to epinephrine in medulla
pineal gland
epiphysis cerebri or pineal body
pinealocytes
- secret melatonin
- diurnal rhythms
- innervated by neurons of the ANS
brain sand
crystallized calcium carbonates and calcium phosphates (pineal)