kidneys Flashcards
what are the basic functions of the kidney?
removing metabolic waste from the ECF
controlling volume of ECF
maintaining optimal volume of solutes
describe the glomerular filtration barrier (GFB)
its composed of a specialised capillary endothelium, basement membrane and podocytes. it allows ECF to be filtered.
what is the average GFR
100ml per min or 144l per day
describe the intercalated cell and principle cell
the principle cell contains the ENaC (epithelium based sodium channel) where potassium can also be secreted out.
if the hydrogen channel in the intercalated cell is open then H+ ions can be secreted out to maintain electroneutrality
describe the function of the sodium potassium two chloride channel
conc gradient is created by the Na K ATPase channel. this allows Na K and Cl to move into the NaK2Cl channel.
potassium recycling occurs through the opening of the potassium ion channel.
Mg and Ca are reabsorbed through the cell junctions
how is glucose reabsorbed and other products?
90% of glucose is reabsorbed in the PCT via SGLT 1/2 transporters and 70% of salt and proteins are reabsorbed too in the PCT
what are the rules of the loop?
the loop of Henle has a thick ascending impermeable duct and a thin descending permeable limb. the thick allows for movement out of sodium potassium and chlorine. this creates a conc gradient allowing for water and salt reabsorption in the thin limb
what do baroreceptors do?
baroreceptors in the aortic arch and carotid sinus will measure pressure.
low BP causes vasoconstriction to the heart increasing SV and pinching of the afferent ateriole. this reduces amount of fluid to be filtered and less reabsorbed
describe the juxta-glomerular apparatus (JGA)
group of cells that interact with the DCT and glomerulus. it maintains the GFR.
macula densa are endothelial cells which sense tubular flow, specifically chlorine.
high sense volume leads to release of adenosine causing constriction of afferent arteriole
reduced sense volume leads to release of renin from granular cells. AGT2 causes constriction of efferent arteriole promoting salt and water reabsorption.
aldosterone is promoted too increasing water and sodium reabsorption in the collecting duct.
describe the calcium conc maintenance
Parathyroid glands detect low calcium levels. leads to release of PTH.
pth instructs bone to undergo resorption releasing calcium, and kidneys to reabsorb more calcium.
vitamin D in the gut is hydroxylated to increase absorption of calcium.
vitamin D–> 25 hydroxy in the liver –> 1,25 hydroxy in the kidney
describe other functions of the kidney
toxin excretion/metabolism
oxygen conc can be low in the tip of loop of henle. due to this it is sensitive to low blood oxygen conc. erythopoietin can then be released to release RBC’s from bone marrow and increase red cell mass
how does the body sense volume?
serum osmolality
reduced stretch from baroreceptors
or reduced stretch in atrial receptors.
these changes are detected by the hypothalamus
describe the action of ADH
ADH is synthesised by the posterior pituitary gland of the hypothalamus, it increases thirst and causes vasoconstriction of vessels
in the collecting duct it allows for aquaporins channels to be inserted, causing water reabsorption.
describe the action of aldosterone
aldosterone is released from the zona glomerulosa of the adrenal cortex, in response to high K levels or AGT2 release.
it acts to increase sodium reabsorption by insertion of ENaC in the collecting duct.
