Glomerulus & Capsule

• This is where glomerular filtrate is formed by the process of ultrafiltration.
• Ultrafiltration:

  1. Blood from the renal artery arrives in afferent arterioles in the renal cortex then passes into the capillaries of the glomerulus.
  2. Hydrostatic pressure (from contraction of LV) is increased as blood passing from an efferent arteriole has a narrower diameter than afferent arteriole.
  3. This pressure forces small molecules such as water, glucose, urea and ions from the capillary into capsule forming glomerular filtrate.
  4. Blood cells and large proteins are too large to pass into the capsule.
• The maximum size of molecule allowed to pass from the glomerulus into the capsule is called the renal threshold.
• The renal threshold is determined by 3 layers between the blood and the filtrate.
• Endothelium of the capillary

  Containing gaps (fenestrations) between the endothelial cells.
• The Basement Membrane

  A mesh of collagen and glycoprotein fibres.
• Podocyte Cells

  The lining of the capsule- also containing gaps to allow filtrate in.