Ultrafiltration and the formation of glomerular filtrate

• Molecules move into the glomerular filtrate through the fenestrated capillary endothelium, the basement membrane and the podocytes
• Molecules which move out of the glomerular capillaries into the glomerular filtrate

  • glucose
  • amino acids
  • water (most)
  • mineral ions
  • urea
• Molecules that can't move out of the glomerular capillaries

  • plasma proteins
  • red blood cells
  • white blood cells
• Factors that resist the movement of small molecules into the glomerular filtrate

  • capillary endothelial cells
  • basement membrane
  • epithelial cells -> podocytes
  • hydrostatic pressure of the fluid in the renal capsule space
  • osmotic pressure of the glomerular filtrate
• Capillary endothelium has spaces between them so filtrate can pass between the cells
• Podocytes have spaces between them due to their branched structure
• Basement membrane

  • thin fibrous layer that separates the capillary endothelium from podocytes
  • formed of connective tissue and proteins
  • acts as a filter - gaps only let small molecules through