Roles of the kidneys
The kidneys process blood and have two key roles within this topic:
| Role | Meaning |
|---|---|
| Osmoregulation | Regulation of the water content of the blood. |
| Excretion | Removal of metabolic waste and excess substances from the blood. |
The nephron is the functional unit involved in urine formation. Small molecules are initially filtered from the blood, useful substances are subsequently reabsorbed, and the fluid that remains forms urine.
Regions of the kidney
- The renal cortex forms the outer region of the kidney.
- The renal medulla forms the inner region.
- The renal pelvis lies towards the centre, collecting urine and funnelling it into the ureter.
Kidneys contain thousands of nephrons. These tubules span the cortex and medulla and ultimately lead towards the renal pelvis.
Exam Tip: Distinguish osmoregulation from excretion: osmoregulation controls water balance, whereas excretion removes metabolic waste and substances present in excess.