nephrons

the structural and functional unit of the kidney, each nephron being capable of forming urine by itself. The nephron consists of the renal corpuscle, the proximal convoluted tubule, the descending and ascending limbs of the loop of Henle, the distal convoluted tubule, and the collecting tubule. Each kidney is an aggregation of about a million nephrons. The specific function of the nephron is to remove from the blood plasma certain end products of metabolism, such as urea, uric acid, and creatinine, and also any excess sodium, chloride, and potassium ions. By allowing for reabsorption of water and some electrolytes back into the blood, the nephron also plays a vital role in the maintenance of normal fluid balance in the body.

The nephron is a complex system of arterioles, capillaries, and tubules. Blood is brought to the nephron via the afferent arteriole. As the blood flows through the glomerulus (a network of capillaries), about one-fifth of the plasma is filtered through the glomerular membrane and collects in the malpighian (Bowman's) capsule, which encases the glomerulus. The fluid then passes through the proximal tubule, from there into the loop of Henle, then into the distal tubule, and finally into the collecting tubule. As the fluid is making its tortuous journey through these various tubules, most of its water and some of the solutes are reabsorbed into the blood via the peritubular capillaries. The water and solutes remaining in the tubules become urine.