KIDNEY Flashcards
what structures are involved in ultrafiltration
glomerulus + bowmans capsule
describe the features of the glomerulus and Bowmans capsule that allow them to perform their function effectively
glomerulus;
afferent arteriole wider than efferent- creates greater hydrostatic pressure than bowmans capsule
gaps in capillary endothelium layer +gaps in basement layer ensure large molecules such as rbs,wbc are kept in capillaries
bowmans capsule has podocytes and pedicils to further filter+stop passing of large molecules PCT
Describe features of bowmans capsule
podocytes
pedicils
Describe features of glomerulus
- filled with capilaries
-basement membrane
Afferent and efferent arterioles
state the 3 processes that occur in the kidney
- ultrafiltration
- selective reabsorption
- osmoregulation
kidney waste product and how it leaves the nephron
The waste product produced by the kidneys is urine.
from collecting duct - ureters- gall bladder. - uretha(out of body)
where do the kidneys receive blood from and where does the blood leave?
The kidneys receive blood from the renal artery and once the blood has been filtered by the kidneys, it leaves via the renal vein.
what mechanism is the kidney reliant on
negative feedback
what happens in selective reabsorption
useful substances that were lost during ultrafiltration (in filtrate)are reabsorbed back into the blood depending on how much is needed.
How is PCT adapted for selective reabsorption
epithelial cells have microvilli to increase SA for reabsorption to occur
lots of mitochondria to provide atp for active transport
outline process of selective reabsorption PCT
. Sodium potassium pump actively moves sodium out of epithelial cells into capillaries leaving low na+ conc in epithelial cells and high na+ conc in filtrate
. concentration gradient formed and encourages movement of na+ to epithelial cells via co-transport proteins - this also moves glucose along
.movement of solute out of filtrate creates high water potential
.movement of solutes into capillaries creates a low water potential
. concentration gradient formed
.water moves from high to low water potential (filtrate to capillaries)
. at end of proximal convoluted tube, filtrate is isotonic to capillaries
where does the MOST selective reabsorption occur
PCT - proximal convoluted tube
function of the loop of henle
To create a low water potential in medulla tissue fluid to ensure urine is more concentrated than our blood (through countercurrent multiplier effect.)
what does the descending limb do
allows water to move out of filtrate as its permeable to water but impermeable to ions and salts.
water moves out of filtrate into tissue fluid then surrounding capillaries
what does ascending loop do
bottom part of ascending loop - diffusion of na+ and cl- into tissue fluid as walls are thin
going up ascending limb- na+ and cl- are actively transported to tissue fluid
No water can leave as its impermeable to water
where is water potential lowest and highest in loop of henle (medulla) and explain why
highest(least solutes present) = top of ascending limb as majority of ions would have been pumped out via active transport and
lowest(most solutes present) = base of loop
as majority of water here has been moved out of filtrate to tissue fluid via osmosis toue to ions that were pumped out of ascending limb (lowering the water potential of tissue fluid)
how does the loop of henle ensure conc of urine is higher than that of blood
loop of henle creates(high solute conc) low water potential in interstitual fluid and higher water potential in filtrate (low solute conc due to active transport in ascending limb)
structure of ascending loop
thick walls at top
thin walls towards bottom
lots of mitchondria for active transport
describe how loop of henle works
- bottom of ascending limb sodium chlorine ions move out via diffusion into tissue fluid
-top of ascending limb ions move out via active transport - no water can be lost here due to it being impermeable to water creates decrease in water potential in medulla - as filtrate travels down descending limb, water leaves via osmosis. ions stay in filtrate as limb is impermeable to ions creating hypertonic solution at base of loop.
call this countercurrent effect.
At top of ascending limb filtrate is hypotonic to blood.
function of DCT
selective reabsorption of any nutrients body still needs(ions) - via active transport
also balances water needs of body based off adh
what happens in collecting duct
water moves out of collecting duct into renal medulla tissue fluid via osmosis (going down renal medulla- solute conc increases so water always moves out) permeability dependant on adh levels
what controls the amount of water lost in urine
ADH which is dependant on water potential of the blood
where is adh produced and secreted
produced - hypothalmus
secreted- pituitary gland
Effect of adh on kidney
adh increases permeability of DCT and collecting duct(more water reabsorbed into blood)= less volume of urine
adh mechanism(fall in water potential of blood-more solutes)
- blood water potential rise
- change detected by osmoregulators in hypothalmus
- more adh released from pituitary gland and carried in blood to collecting duct
- adh binds to cell receptors trigerring formation of camp
- causes vesicle to fuse with membrane along collecting duct
- fusing of vesicle and membranes allows aquaporins to be inserted in cell membrane
- makes collecting duct more permeable
what detects changes in blood water potential
osmoreceptors in hypothalmus
adh mechanism(fall in water potential of blood-more solutes)
- high ion conc in blood decreases the water potential of the blood
- this change is detected by osmoreceptors in the hypothalamus
- which sends nerve impulses to pituitary gland to release more adh in blood
- adh binds to receptors on collecting duct -triggering formation of cAMP
- this causes vesicles and membrane to fuse
- releases aquaporins into membranes
- makes membrane more permeable to water
- more water can move out of collecting duct into medulla tissue fluid + capillaries via osmosis.
what happens when water is in short supply in body
- high ion conc in blood decreases the water potential of the blood
- this change is detected by osmoreceptors in the hypothalamus
- which sends nerve impulses to pituitary gland to release more adh in blood
- adh binds to receptors on collecting duct -triggering formation of cAMP
- this causes vesicles and membrane to fuse
- releases aquaporins into membranes
- makes membrane more permeable to water
- more water can move out of collecting duct into medulla tissue fluid + capillaries via osmosis.
- urine smaller volume and more concentrated
what happens when water is in excess supply in body
- low ion conc in blood increases the water potential of the blood
- this change is detected by osmoreceptors in the hypothalamus
- which reduces nerve impulses to pituitary gland to inhibiting secretion of adh
- reduction of cAMP levels
- less aquaporins released into membranes
- membrane less permeable to water
- more water in urine- larger volume of urine, less concentrated
what effect does adh have on body
more adh = more permeable collecting duct walls= more water reabsorbed into cells= smaller volume of concentrated urine
how does adh increase permeability of cells lining the PCT and collecting duct to water
- stimulus of increased adh from pituitary gland
- adh binds to receptors on outer surface membranes(pct and collecting duct)
- triggers formation of cAMP
- which causes vesicles and inner membranes to fuse
- aquaporins(water based channels) released into membrane
- increasing tubules permeability of water
- water moves out of tubules and into medulla tissue fluid then capillaries
what does “ cAMP is a secondary molecule” mean
A secondary molecule is a molecule that relays signals recieved at cell surface receptors to molecules inside the cell- causes cascade of events.
How does production of cAMP trigger molecules inside cells
- vesicles in cells lining collecting duct fise with cells in contact with tissue fluid of medulla
- when fused with membrane - aquaporins inserted into membrane - making them more permeable to water
explain importance of osmoregulation
Water levels and mineral ions in the blood are controlled to keep the concentrations the same inside the cells as around them. This protects cells by stopping too much water from entering or leaving them by osmosis.
