How does your kidneys filter waste from your bloodstream?

The kidneys filter blood through tiny units called nephrons, of which each kidney contains about one million. Blood enters the nephron through a bundle of capillaries called the glomerulus, where pressure forces water, salts, glucose, and waste products like urea out of the blood and into a cup-shaped structure called Bowman's capsule. This liquid is called the filtrate. As the filtrate travels through the tubules of the nephron, useful substances like glucose, water, and essential salts are reabsorbed back into the bloodstream. What remains, including urea and excess salts, becomes urine. This urine then flows to the collecting duct, down to the renal pelvis, through the ureters, and into the bladder for excretion.