Kidneys

Homeostasis

maintaining a stable internal environment within set limits

Negative feedback

Restores system to their original level by reversing any change

Functions of kidneys (4)

Excretion of nitrogenous waste

Osmoregulation

Ultrafiltration

Selective reabsorption

Label A-H

Renal artery

Renal vein

Ureter

nephron

cortex

medulla

pelvis

Pryamid??

What is the basement membrane

Sieve at base of Bowmans capsule - only allowing small molecules

Describe ultrafiltration

Driven by hydrostatic pressure from the afferent arteriole

Basement membrane acts as a molecular sieve to filter out large molecules

Small molecules such as water, glucose, amino acids, urea and vitamins then move into PCT as glomerular filtrate

How are PCT adapted to selective reabsorption

Microvilli - increase surface area

Plenty mitochondria - provide ATP

Membrane bound transport protein - carry out selective reabsorption

What substances are reabsorbed in PCT

Glucose, amino acids, most water and ions from filtrate back into blood

unnecessary

oops

Deamination

Removal of amine group to leave ammonia and pyruvic acid

What do fish, animals and birds each excrete nitrogen as

Ammonia diffuses into water

Urea in urine

Uric acid

Label A-D

Afferent arteriole

Efferent arteriole

Descending LOH

Ascending LOH

Vasa recta

Surrounding capillary network

Delivers nutrients and oxygen

How is each molecule selectively reabsorbed

Glucose + amino acids - co-transport with Na+

Water - osmosis because solutes leave

Urea - 50% reabsorption by diffusion

How does the loop of henle work

Ions are pumped out actively from ascending limb causing solute potential in medulla to increase

Water moves out descending limb into the blood via osmosis

Descending limb then becomes even more concentrated as it goes down

What is each loop permeable to

Descending loop permeable to water so it can move out

Ascending loop impermeable so ions move out

What happens when there’s a decrease in water potential in the blood plasma

Osmoreceptors in hypothalamus detect decrease in water potential

Posterior pituitary releases ADH

Cells of DCT and collecting duct become more permeable due to aquaporins fusing will cell membrane

More water then reabsorbed from CD into blood

Small volume of concentrated urine then produced

What happens when an increase in water potential is detected

Osmoreceptors in hypothalamus detect

Posterior lobe of pituitary stops release of ADH

DCT and CD become less permeable as aquaporins move out the membrane

Less water reabsorbed into blood

Large volume of dilute urine produced

Treating kidney disease (4)

Low protein diet

Drugs

Dialysis

Kidney transplant

Drugs to reduce blood pressure

Calcium channel blockers

Beta blockers - adrenaline

Describe haemodialysis

Blood is taken from arm and places in countercurrent to dialysis fluid in a machine

Small molecules move through pores but not large molecules

Blood is then returned to the vein

ions and urea diffuse down concentration gradients

Continuos ambulatory peritoneal dialysis

Dialysis fluid passes into abdominal cavity

after 40 mins the fluid is drained form the abdomen into a bag