**1. Glomerulus Filtration

What are the 3 mechanisms of urine formation?

• Glomerular filtration

  • from blood plasma —> nephron

  • in Bowman’s capsule

• Tubular reabsorption

  • from lumen of tubule —> capillary

  • in proximal, distal, collecting duct and LoH

• Tubular secretion

  • from capillary —> lumen of tubule

  • in proximal, distal, collecting duct and LoH

What is the movement of glomerulus filtration?

Movement of water and solutes from

• Plasma in glomerulus —>

• Glomerular-capsule membrane —>

• Capsular space of bowman’s capsule

What is glomerular filtrate?

The fluid constituents that pass from blood plasma in glomerulus —> urinary space of Bowman’s capsule

What is proteinuria?

The presence of abnormal amounts of protein in urine

What are the 3 physical barriers which the filtrate passes?

• Capillary endothelium of glomerulus

• Inner layers of Bowman’s capsule

• Filtration slits, made by

  • Fenestrated glomeruluar endothelium

  • Glomerular basement membrane

  • Podocytes with cellular extensions

Filtration Pressure in Glomerular Filtration

• What

• Calculated as

What: The pressure that drives fluid out of capillaries

Calculated as: The difference between blood hydrostatic pressure and osmotic pressure from plasma proteins in capillaries

Filtration Pressure in Glomerular Filtration

• What generates the osmotic pressure that opposes filtration in glomerulus?

Plasma proteins in capillaries generates osmotic pressure that pulls water back into capillaries

What is renal autoregulation?

Kidney’s ability to maintain stable GFR and blood flow despite changes in systemic blood pressure

What causes vasoconstriction in renal autoregulation?

Increases in sympathetic nerve activity and vasoconstrictors like angiotensin II

What can excessive renal vasoconstriction lead to?

It reduces glomerular filtration to the point of renal failure

Why is a high GFR to urine flow good?

It allows for

• Continuous filtration of plasma

• Rapid removal of unwanted substances

What can substances be rapidly eliminated by urine?

If they pass through glomerular filtration barrier and not reabsorbed from renal tubules

What are the 2 factors influencing the glomerular filtration

• Hydrostatic pressures in

  • afferent arteriole, glomerulus, Bowman’s capsule

• Molecular size of substances in blood

Glomerular Filtration Rate (GFR)

• What

• Expressed as

• Measured using

• Method

What: The volume of glomerular filtrate formed by both kidneys per minute

Expressed as: ml/min/kg bodyweight

Measured using: Insulin (exogenous substances) and creatinine (endogenous substances)

Method: Concentration = Mass / Volume