How does your kidney filter waste from your blood?

Blood enters the kidney through the renal artery, which branches into tiny capillaries that lead to about one million filtering units called nephrons. Each nephron contains a glomerulus, a small cluster of capillaries where blood pressure forces water, salts, glucose, urea, and other small molecules out of the blood and into a cup-shaped structure called Bowman's capsule. This filtered fluid then travels through a series of tubules where useful substances like glucose, water, and essential salts are reabsorbed back into the bloodstream. What remains, including urea and excess salts, becomes urine. The urine collects in the renal pelvis and drains through the ureter to the bladder for excretion.