Endocrine system Flashcards
endocrine system: main features
- has endocrine glands-> secrete hormones into bloodstream/ tissues
- regulate homeostasis, coordinate growth and development
how does hormones interact general:
specific receptors to alter biological activity of target cells
nervous system vs endocrine system general:
ns: rapid response, short duration
es: slow response, longer duration
endrocrine glands: general features
ductless glands, secretory cells release hormones into blood stream/ tissues to target cells
list main glands:
pituitary (hypophysis), pineal, thyroid, parathyroid, pancreas, adrenal
ovaries, testes
hormone secretion happens by:
signals from nervous system, chemical change in the blood, other hormones
types of hormones:
proteins, steroids, amines
eg of hormone secreting glands: protein
hypothalamus, pituitary, thyroid, parathyroid, pancreas, enteroendrocrine cells of digestive tract
eg of hormone secreting glands: steroids
ovaries, testes, adrenal cortex
eg of hormone secreting glands: amines
adrenal medulla, thyroid
steroids are derived from:
cholesterol
amines are derived from: and eg
amino acids and derivatives, eg: norepinephrine, epinephrine
location/ features: pineal glands
posterior extremity of 3rd ventricle (aka epiphysis cerebri)
- secretes melatonin -> regulates circadian, seasonal biorhythm
- increases during darkness
location/ features: pituitary gland
hypophysis, base of brain sella turcica, connected to hypothalamus via infundibulum
pituitary gland sections: anterior
adenohypophysis
pars distalis
pars tuberalis
pars intermedia (feotal dev)
pituitary gland sections: posterior
neurohypophysis
pars nervosa
infundibulum
blood supply: pituitary gland
superior/ inferior hypophyseal arteries (branches of internal carotid aa.)
hypophyseal portal system: primary and secondary capillary plexus
anterior pituitary: general function
regulates endocrine glands and some non-endorcrine tissues
list tropic hormones:
- adrenocorticotropic h. (ACTH)
- thyroid stimulating h. (TSH)
- follicle stimulating hormone (FSH)
- luteinising h. (LH)
list non-tropic hormones:
growth hormones (GH) prolactin (PRL)
pituitary glands: tissue
cells: cords and nests, numerous capillaries
50% chromophobes
50% chromophyles
- acidophils 40%
- basophils 10%
hormone secreted/ features: acidophils
somatotropes (GH)
- stimulates growth
lactotropes (PRL)
- lactation
hormone secreted/ features: basophils
corticotrope (ACTH)
- stimulate adrenal cortex
gonadotropes (FSH, LH)
- regulates ovary/ testes
thyrotropes (TSH)
- stimulates thyroid
hormone secreted/ features: chromophobes
- unstained/ weakly stained cells
- most dormant/ recently degranulated chromophils
- stem cells of secretory cells
eg. abnormal amounts of growth hormone
- dwarfism, lil growth hormone: from tumour suppressing, still in proportion
- gigantism, extra growth hormone: long bones grow more
- acromegaly: after long bones fuse increase in growth hormone, disproportionate
posterior pituitary: general features/ function
storage site for neruro-secretions of hypothalamus
- fibroblasts, mast cells, pituicytes (specialised glial cells)
posterior pituitary: secretions/ function
- antidiuretic hormone (ADH): resorption of water
- oxytocin: contraction of smooth muscle in uterus/ myoepithelial cells in breast
contained in neurosecretory vesicles: Herring bodies
hypothalamus: features/ function
regulates pituitary gland function
- major control centre for ANS
- regulates blood pressure, body temp, fluid, electrolyte balance, body weight, appetite
hypothalamus hormones:
ADH, oxytocin,
- polypeptides control secretion of hormones from anterior pituitary
location/ features: thyroid gland
anterior neck, inferior to thyroid cartilage
- R/L lobe connected by isthmus/ sometimes 3rd pyramidal lobe
- surrounded by septa (capsule)
thyroid gland: functional unit
secretory follicle
blood supply: thyroid gland
superior (external carotid)/ inferior (thyrocervical trunk) thyroid arteries, thyroid ima artery
secretory follicle: features/ function
- simple cuboidal- low columnar epithelium forms wall
- contain gel-like mass: colloid
- colloid contains thyroglobulin, inactive storage of T3 T4 hormones
list types of thyroid cells
follicular cell (principal cell), parafollicular (C) cell
features/ secretion: follicular cells
spherical nuclei, slightly basophilic cytoplasm,
- produces T3 (triiodothyronine) T4 (thyroxine) -> regulates cell/ tissue metabolism, heat production, influences body growth/ dev
- regulated by TSH from ant. pituitary
features/ secretion: parafollicular cells
periphery of follicular epithelium, larger cells with pale cytoplasm
- secretes calcitonin (lowers blood Ca levels)
- regulated by blood Ca levels
parathyroid gland: location/ general features
2 pairs (superior/inferior) small glands
- posterior surface of lateral lobes of thyroid
- has septa (ct capsule)
- well vascularised
list types of cells in parathyroid:
chief and oxyphil cells
features/ secretion: chief cells
more common parathyroid cells, secretes (parathyroid hormone) PTH
- increases blood Ca/ Mg
- reduces phosphate
- with age replaced by adipose cells
location/ general features: adrenal glands
flattened triangular shaped organs superior to kidneys
- within ct capsule (trabeculae)
- 80-90% cortex
- medulla centre
blood supply: adrenal glands
superior (inf. phrenic artery), middle (abdominal aorta) and inferior (renal artery) suprarenal arteries
adrenal cortex layers:
outer-> inner
- zona glomerulosa
- zona fasciculata
- zona reticularis
steroid hormones/ function: zona glomerulosa
mineralcorticoids:
- aldosteron: regulates Na, K balance, homeostasis, water balance
steroid hormones/ function: zona fasciculata
glucocorticoids:
- cortisol: regulate glucose/ fatty acid metabolism
steroid hormones/ function: zona reticularis
gonadocorticoids:
- weak androgens, masculising effect (insignificant usually)
adrenal medulla: features
large chromaffin cells in strands or sml clusters (postsynaptic neurons)
- capillaries and venules in intervening spaces
adrenal medulla: hormones/ function
- epinephrine and norepinephrine
- sympathomimetic effect (similar to sympathetic div of ANS)
- increase heart rate/ blood pressure/ sweating, respiration and decreases digestion
- fight or flight response
- glucocorticoids
features/ location: pancreas
elongated flattened shape,
- btw duodenum (R)/ spleen (L)
- both endocrine/ exocrine gland
pancreas exocrine part:
pancreatic islets of Langerhans scattered among acini
blood supply: pancreas
splenic artery, pancreatic artery,
- ant/post. superior pancreaticdiodenal
- ant/post. inferior pancreaticdiodenal
features: islets of Langerhans
islets form round/ isolated cell clusters surrounded by fine capsule (reticular fibres)
- network of blood capillaries
list pancreas secretions:
alpha, beta, delta (D) and F cells
secretions: alpha and beta cells
a: glucagon- increase blood glucose levels
b: insulin- decrease blood glucose levels, essential for cell growth
absence/ inadequate levels of insulin:
diabetes mellitus
secretions: D and F cells
D: somatostatin: inhibits insulin/ glucagon secretion
F: pancreatic polypeptide- inhibits somatostatin (D) secretion, gallbladder contraction, secretion of digestive enzymes by pancreas
list gonads and type of hormone:
ovaries, testes
steroid hormones
hormones: ovaries
estrogen, progesteron:
regulate menstrual cycle, maintain pregnancy, prepare mammary glands for lactation, promote/ maintain secondary sex characteristic,
- inhibin inhibits secretion of FSH
hormones: testes
testoterone: stimulates drop of testes, regulates sperm production, maintenance of secondary sex characteristics,
- inhibin
