This video explores how the kidneys filter blood to remove wastes and excess fluid from the body, maintaining a healthy balance of water and salts in the blood.

Physician Richard Lifton explains that as fluids (mostly water) from blood move through the kidney, almost all of the water, along with salts and nutrients the body needs, are reabsorbed by the blood. The remaining fluid and wastes become urine.

Lifton uses a fish tank being filled with water and salt to demonstrate how much liquid the kidney filters in a day: about 170 liters, of which only about 1 liter ends up in the urine. He also uses a 3D model to illustrate anatomical components of the kidney, including the nephron, the proximal tubule, the renal medulla, the loop of Henle, the distal convoluted tubule, and the cortical collecting duct.

This clip is from a 1998 Holiday Lecture Series, Of Hearts and Hypertension: Blazing Genetic Traits.