Renal Function and Filtration

Urine Formation

• Urine formation is determined by the process of glomerular filtration, followed by tubular reabsorption and tubular secretion.

Filtration Rate

• The filtration rate in the kidneys is determined by the following factors:
  • Blood pressure
  • Glomerular capillary pressure
  • Bowman's capsule pressure
  • Plasma oncotic pressure
  • Hydraulic permeability of the glomerular capillary wall

Ultrafiltrate Composition

• The ultrafiltrate in the kidneys has a composition similar to blood plasma, but without proteins and other large molecules.
• It contains water, ions, glucose, amino acids, and other small molecules.

Glomerular Filtration Intensity

• The intensity of glomerular filtration is determined by the pressure difference between the glomerular capillary pressure and the Bowman's capsule pressure.
• The difference in pressure forces the fluid and small molecules out of the capillary and into the Bowman's capsule.

Reabsorption Intensity

• The proximal convoluted tubule (PCT) is the part of the nephron responsible for the intensity of reabsorption.
• Most of the reabsorption of water, ions, and nutrients occurs in the PCT.