Nephron

About the Nephron

The nephron is the microscopic functional unit of the kidney, and each kidney contains around a million of them. Each nephron begins with a renal corpuscle, made up of a tuft of capillaries called the glomerulus enclosed in Bowman capsule, where blood pressure forces water and small molecules out of the blood while retaining cells and most proteins. The filtrate then flows through the proximal convoluted tubule, which reabsorbs most of the water, glucose, amino acids, and sodium, the loop of Henle, which creates a concentration gradient in the medulla that allows urine to be concentrated, the distal convoluted tubule, and finally a collecting duct. Hormones fine tune this process: antidiuretic hormone controls water reabsorption in the collecting ducts, and aldosterone regulates sodium and potassium. The juxtaglomerular apparatus senses blood pressure and releases renin. Nephrons cannot regenerate, so their gradual loss underlies chronic kidney disease, and the glomerular filtration rate is the standard measure of kidney function.