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Kidneys - Urine Production

Each kidney contains millions of very small structures called nephrons. There are two stages in the process of urine production. These stages happen in every nephron.

Ultrafiltration

Ultrafiltration

  • The blood capillaries form a tightly knotted cluster, squeezing out small particles from the blood.
  • The blood is filtered and all water, urea and salts are removed from the blood.
  • Blood cells and proteins remain in the blood as they are too big to move across the capillary walls.
Selective reabsorption

Selective reabsorption

  • Useful substances, including glucose, some salts and most water, are reabsorbed back into the bloodstream.
  • This leaves all urea, excess salts and excess water collected in the nephron.
  • This mixture forms urine, which is collected by the kidneys and travels to the bladder to be stored and then excreted.
Jump to other topics
1

The Nature & Variety of Living Organisms

2

Structure & Functions in Living Organisms

3

Organism Functions

3.1

Respiration

3.2

Gas Exchange

3.3

Transport

3.4

Excretion

3.5

Coordination & Response

4

Reproduction & Inheritance

5

Ecology

6

Biological Resources

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