Nephron structure Flashcards
What arteriole enters the nephron?
Afferent
What is the glomerulus?
a bundle of lots of capillaries, made up when the afferent arteriole branches out forming lots of capillaries
Where is the glomerulus found?
the renal capsule
What branches out from the renal capsule?
the proximal convoluted tubule
What is the function of the nephron?
filter the blood to remove waste and selectively reabsorb useful substances back in to the blood
What does urine not contain? (in a healthy person)
proteins and blood cells- too big
glucose - is selectively reabsorbed
What does urine contain?
mineral ions
water
urea
small substances
What happens in the glomerulus?
ultrafiltration forces out water and small molecules due to high hydrostatic pressure. These enter the renal capsule
What happens at the loop of Henle?
Na+ gradient maintained, so water can be reabsorbed by the blood
What arteriole leaves the renal capsule?
efferent
How are the cells lining the proximal convoluted tubule adapted to it’s function?
- cells have microvilli that create large SA for reabsorption of glucose
- cells have lots of mitochondria which produce the ATP needed for active transport
Why is the [Na+] low in the PCT cells?
Na+ is actively transported into the blood
Why does a low concentration of Na+ ions in the cells lead to glucose being absorbed?
Na+ can diffuse down its conc. gradient through a co-transport protein. The co-transport protein carries glucose also
Why cant water move out in the ascending limb of the loop of Henle?
the walls are impermeable
What happens in the ascending limb?
Na+ ions are actively transported out, into the interstitial space
What does the increase in Na+ ions do?
lowers water potential in interstitial space
What happens at the base of the loop of Henle?
some Na+ ions diffuse into the interstitial space
Describe the liquid that enters the distal convoluted tubule
very dilute (as Na+ ions moved out, however still has higher WP than medulla so moves out by osmosis
How is glucose reabsorbed in the PCT?
- Na+ actively transported out of Epithelial cells lining PCT (into blood)
- forms conc. gradient, so Na+ diffuse down conc gradient into epithelial cells from the lumen
- through co-transport protein, which takes glucose with it
- diffuses into blood via facilitated diffusion
How is water reabsorbed in the Loop of Henle?
- Na+ actively transported out of ascending limb, which is impermeable to water
- low water potential in the medulla
- water moves out of descending limb, into the medulla by osmosis
- water potential in the medulla decreases as you go down the loop of Henle so WP gradient maintained
How is the PCT adapted for its function?
- microvilli; large SA for reabsorption
- infoldings; large SA to transfer substances into capillaries
- lots of mitochondria for AT
How might length of loop of Henle change depending on the environment they live in? why?
drier environments = longer loop of Henle
so more water absorbed along the whole length
What is the gross structure of the kidney? (go from the outside in)
- capsule
- cortex
- medulla
- pelvis
- ureter
