Kidneys and excretion
Excretion is removing the waste products of metabolism. The lungs excrete carbon dioxide; the kidneys excrete urea, excess water and excess ions as urine. Urea is made in the liver by deamination of excess amino acids. In each kidney nephron, blood is filtered under high pressure in the glomerulus (ultrafiltration): small molecules pass into the tubule. Then all glucose, most water and some ions are selectively reabsorbed. What's left flows to the bladder. Kidney failure is treated by dialysis or a transplant.
≈ 40 min