Physiology of the Kidneys

Urine is formed in three steps: filtration, reabsorption, and secretion.

Glomerular filtration is the renal process whereby fluid in the blood is filtered across the capillaries of the glomerulus.

Regulation of GFR requires both a mechanism of detecting an inappropriate GFR as well as an effector mechanism that corrects it.

Tubular reabsorption is the process by which solutes and water are removed from the tubular fluid and transported into the blood.

Hydrogen, creatinine, and drugs are removed from the blood and into the collecting duct through the peritubular capillary network.