LOH, DCT and collecting duct Flashcards
what are limits for the osmolarity of urine determined by
osmolarity of the renal medulla
what is the loop of henle
juxtamedullary nephrons drop down into the renal medulla and then return to the cortex
characteristics of descending limb of LOH
lacks ion pumps
expresses lots of aquaporins
very permeable to water
permeability of thick and thin ascending limb of LOH
not permeable to water
what does active transport of ions out of the thick ascending limb lead to
osmotic transport of water out of the descending limb
2 steps in the loop of henle
static effect
fluid flow
what is the static effect
active transport if solute out of ascending limb to make interstitial space hyperosmotic and draws water out of descending limb making filtrate more concentrated
what is fluid flow
as filtrate is continually produced, new tubular fluid enters the descending limb and pushes the fluid at higher osmolarity down the tube
effect on osmotic gradient as static effect and fluid flow steps repeated
steadily multiplies down the tube
what is the capillary network surrounding the juxtamedullary LOH called
vasa recta
function of the vasa recta
supply oxygen and nutrients to the medulla
where does the vasa recta run
parallel to the limbs of the LOH
blood flow in the vasa recta
blood flows in opposite direction to the filtrate and hairpin loop slows blood flow down
components of the counter-current multiplier
specialised peritubular capillaries (vasa recta)
loop of henle
what allows urea to escape the collecting duct and be recaptured by the descending LOH
urea channels in the medulla
what is responsible for 50% of the osmotic gradient
urea recycling
recycling process of urea
antidiuretic hormone upregulates urea channels in the inner medullary collecting ducts allowing more urea to flow passively into the interstitial fluid and back into thin descending LOH
what controls water balance
endocrine
ADH
where is ADH made and packaged
neuron
where is ADH stored
posterior pituitary
what does ADH do
binds to specific membrane receptor
receptor activates cAMP 2nd messenger system
cell inserts aquaporins into apical membrane
water absorbed by osmosis into the blood
characteristics of diluted urine
excessive drinking
no ADH
no aquaporins
characteristics of concentrated urine
dehydration
increased ADH
increased aquaporins
enzyme that maintains sodium-potassium gradient
sodium potassium ATPases
what allows passive diffusion of ions between principle cells and filtrate
leak channels on apical side of principle cells
characteristics of principle cells
asymmetrical arrangement of Na, K ATPase
no microvilli
impermeable to water without ADH - not linked to reabsorption of sodium
what regulates the secretion of K and reabsorption of NA in principle cells
aldosterone
what does the zona glomerulosa secrete
mineralocorticoids
what hormone is released in response to decreased calcium in the blood
parathyroid hormone = PTH
what does PTH decrease in the proximal tubule
reabsorption of phosphate
what does PTH increase in the ascending loop of henle, distal tubule and collecting tubule
reabsorption of calcium
