Renal System - Ultrafiltration + Reabsorbtion

Question 1

What is ultrafiltration

Answer 1

Involve:
-glomerulus + Bowman capsule + afferent + efferent arteriole

-high hydrostatic pressure in blood of glomerulus against osmotic pressure in bowman capsule push nutrients + urea out into Bowman’s capsule
-becomes renal filtrate and go to PCT

Question 2

Adaptation for ultrafiltration (arteriole)

Answer 2

-efferent arteriole lumen narrow than afferent
- contraction creates pressure gradient - push pressure back to glomerulus - maintain high hydrostatic pressure + avoid damaging other blood vessel

Both can change diameter - affect glomerular filtration rate

Question 3

Adaptation for ultrafiltration (barrier)

Answer 3

Capillary wall semi permeable - only small molecules through (aa, glucose, urea no RBC)

Basement membrane negatively charged - all small protein negative charge - reflect back, glucose ions not

Podocyte- has slits around wall - can open or close to change surface area - affect glomerular filtrate rate - allow small molecules in only

Question 4

What is selective reabsorption

Answer 4

-nutrients + ions from filtrate re absorbed back into blood (useful)
-while certain things (urea) excreted

Question 5

Total substance reabsorbed

Answer 5

Water - 99%
NaCl - 99.5%
Glucose + amino acid - 100%
Urea - 50% (for urea recycling)

Question 6

Reabsorption at PCT

Answer 6

-Water diffuse to PCT cells cytoplasm via osmosis, then diffuse to blood plasma (65% reabsorbed)
-water potential difference since ions + substance leave

-Ions reabsorbed by facilitated diffusion + primary active transport to PCT cells (65%). Glucose + amino acid co-transport with ions to cell (100%)
-Both facilitated diffusion or primary active transport to blood

Question 7

Adaptations for PCT

Answer 7

-Microvilli in glomerular lumen + basal channel to blood vessel = SA increase
-Lots of mitochondria in PCT cells via = active transport
-lots of RER + Golgi body = more channel or carrier protein

Question 8

Reabsorption - Loop of Henle

Answer 8

Follows counter current multiplication

1) descending limb permeable to water only, ascending to ions only

2)ions facilitated diffuse out of thin limb + active transport out of thick - into medulla interstitium (medulla become low water potential) - absorbed by vasa recta

3)water in descending limb diffuse out (it is hypotonic) to interstitium. Absorbed by cast recta. Descending limb not permeable to ion - maintain water potential gradient