The kidney and the urinary systemSpec 2.72B, 2.73B
The kidneys do two jobs. Excretion: they remove urea from the blood. Osmoregulation: they control the water content and the ion content of the blood. Both jobs happen as the kidneys make urine.
- Excretion: urea is filtered out of the blood and is not taken back, so it leaves the body in urine.
- Osmoregulation: the kidney changes how much water (and how many ions) it reabsorbs back into the blood, so only the excess is lost in urine.
| Part | Function |
|---|---|
| Kidneys | Filter the blood and make urine |
| Renal artery | Brings blood to the kidney |
| Renal vein | Takes blood away from the kidney |
| Ureters | Tubes that carry urine from the kidneys to the bladder |
| Bladder | Stores urine |
| Urethra | Tube that carries urine out of the body |
(opens full size in a new tab)Common mistake:
The ureter carries urine from the kidney to the bladder. The urethra carries urine from the bladder out of the body. Do not swap them.