Nephron

What is role of Loop of Henle

Decrease water p in medulla

What does this allow?

Allows H2O removed from urine as it travels through collecting duct

How is water removed from urine?

Loop of H achieves this through counter current multiplier system

What is loop of Henle made up of

Descending + ascending limb

What are adaptations of descending L?

Thin and permeable to ions and water

What are adaptations of ascending L?

Thick and impermeable to water contains protein pumps for pumping out ions

What is region out of Loop of Henle called

Interstitial space

What does the ascending L do?

Pumps Na+ and Cl- into interstitial space - it is impermeable water

What does this do?

Increase ion conc and reduces water p In interstitial fluid

What does the descending L do?

Permeable to water ions so Na + diffuses in and water diffuses out

What does this lead to?

Descending L and interdigital space have lower water p than ascending L

What is ion conc like at bottom of ascending limb?

High

If ion conc is high at the bottom what can sodium do?

Move out alone by diffusion

What is going on higher up ascending L

More Na+ is actively pumped into interstitial space

Why is this?

More Na+ bottom of ascending limb

Bottom of interstitial space has more Na+ the top

What is ion conc and water p like in medulla

High Na+ ion conc but low water p

What is it cakaked when loop of H is able to reduce water p

Counter current multiplication

What is counter-current multiplication

Fluid flows in opp directions to max diffusion

What are adaptations of distal convoluted tubule?

Mitochondria - active transport and absorb min ions - ensures blood has correct concs

Microvilli

Make sure blood is correct pH

What happens after min conc is balanced?

DCT filtrate = collecting d

Where are many of ions removed from filtrate?

Loop of Henle

Why is this?

Water p of filtrate in collecting d is quite high

What is water p like in collecting d?

High compared to interstitial f of medulla

How does filtrate move out of collecting d?

By osmosis into interstitial fluid

Why does fluid in collecting d get more and more conc?

Medulla’s water p gets lower

What is kangaroo rat?

Organism specialised to live without a water supply

Behavioural adaptation of kangaroo rat

Stays underground during day - reduced need to use water for cooling

Physiological adap KR

Get most of water from food

Water produced in metabolic reactions resp and condensation

Oxidative p - use oxygen as final e acceptor

What % does rat get it’s water from these reactions

85%

Anatomical adaptation

More juxtamedullary nephrons

What is difference between cortical and juxtamedullary nephrons?

Cortcial - short loop of H

Juxtamedullary - long loop of H goes into medulla

KR have longer loops of H

Longer than descending L - diffusion of water and ions can occur

= further in medulla conc of looop of H and interstitial f increases

What does a longer loop of H mean for kangaroo rat?

Diffsuion can happen over longer d

What does this mean?

More water can diffuse out of collecting ducts + urine can become even more conc

The adapatations to their tubular cells KR

Have more infoldings - greater reabsorption of ions + water that follows ions

Cells also have more mitochondria than other animals specialised lots of act t or ions and water