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Homeostasis - kidneys and water balance

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How the kidney works

Each kidney contains about a million tiny structures called nephrons. A nephron has a cup-shaped Bowman's capsule leading into the renal tubule. The two sections of each nephron extend across the two different regions of the kidney:

  • the Bowman's capsules are found within the outer cortex region
  • the renal tubules run from the cortex into the darker medulla


How does the kidney balance the blood?

Placed end to end, the nephrons of one kidney would stretch about 8 km. Their function is to remove waste products such as urea and balance the water and mineral ion concentration of the blood. How does the process work?

A branch of the renal artery supplies the nephrons with blood. In the Bowman's capsule, the artery splits up into a network of capillaries called the glomerulus. These capillaries join into a single vessel again as they leave the capsule, and then split into a second set of capillaries that are wrapped around the renal tubule. The blood leaves the tubule in the renal vein.

Water regulation is controlled by Anti-Diuretic Hormone (ADH). For more information see ADH and control of the water balance.