KIDNEYS Flashcards
what is the function of the kidneys
to excrete waste (urea)
to regulate blood water potential
how does blood enter the kidneys
through the renal artery
where does ultafiltration tank place
the glomerulus and bowmans capsule
which arteriole takes blood into the glomerulus
afferent arteriole
which arteriole takes filtered blood away the glomerulus
efferent arteriole
how do you generate high pressure in the glomerulus causing ultrafiltration
The afferent arteriole (opening) is wider than the efferent arteriole (closing) therefore blood is at high pressure in glomerulus
what is passed onto bowmans capsule in ultrafiltration
liquid and small molecules into bowmans capsule
what are the 3 layers the liquid and small molecules have to pass through to get from the capillary to the bowmans capsule
the capillary wall
the basement membrane
epithelium of bowmans capsule
what is the glomerular filtrate and what does it consist of
the large molecules that can to fit through the membrane into the bowmans capsule and therefore stay in the blood
eg proteins and blood cells
what happens next to glomerular filtrate from stage 1
it passes along the nephron to the PCT (proximal convoluted tubule), loop of Henle and DCT (distal convoluted tubule) where selective reabsorption happens
what does the PCT wall have on it
microvilli
providing a large SA for the reabsorption of useful materials from the glomerular filtrate into the blood
What is reabsorbed along the PCT and how
glucose is selectively reabsorbed
by active transport and facilitated diffusion
what is urine made up of
water urea dissolved salts hormones excess vitamins
where is water reabsorbed
PCT
Loop of henle
DCT
Collecting duct
state 2 ways water is lost
urea
sweat
what is osmoregulation
the regulation of water potential
what happens if water potential is too low
if water potential is too low
more water reabsorbed by osmosis into blood from nephron
Means urine is more concentrated, so less water lost during excretion
what happens if water potential is too high
if water potential is too high
less water reabsorbed by osmosis into blood from nephron
Means urine is more dilute, so more water lost during excretion
where along the nephron is water potential regulated
loop of henle
DCT
collecting duct
what 2 limbs make uptake loop of henle
the ascending and descending limb
what is the gap called in between the 2 limbs
the medulla
how does the loop of henle maintain the Na+ ion electrochemical gradient
At the top of the ascending limb Na+ ions are pumped out by activeT
Ascending limb impermeable to water so water remains inside
This movement of Na+ ions into medulla lowers the water potential
Then water moves via osmosis (high to low) from the descending limb into the medulla (descending limb = permeable to water)
At the bottom of the ascending limb Na+ ions diffuse into the medulla, again lowering water potential
Water then moves out of the DCT by osmosis and is reabsorbed into the blood
Water also moves out of the collecting duct
what cells monitor water potential of the blood
osmoreceptors
where in the brain is blood water potential regulated
hypothalamus
when your dehydrated what happens to blood ADH levels
Water content of blood drops
Water potential drops
Osmoreceptors in hypothalamus detect a change
Posterior pituitary gland is stimulated to release MORE ADH into blood
More ADH means DCT and collecting duct more permeable to water
More water is reabsorbed from tubules into medulla and blood via osmosis
A small amount of conc urine is produced
Meaning less water lost from the body
when your hydrated what happens to blood ADH levels
Water content of blood increases
Water potential increases
Osmoreceptors in hypothalamus detect a change
Posterior pituitary gland is stimulated to release LESS ADH into blood
Less ADH means DCT and collecting duct less permeable to water
Less water is reabsorbed from tubules into medulla and blood via osmosis
A large amount of dilute urine is produced
Meaning more water lost from the body
