- Each of the 1 million nephrons in each kidney filters a tiny amount of blood plasma. Combined they filter 120mL of plasma each minute.
How it works:
- The high blood pressure of the blood traveling through the arteries toward the kidney causes plasma to pass through the capilary walls of the glomerulus into the Bowman's Capsule.
- Filtered Blood enters the tubules of the kidney. Filtrate contains substances that are still needed by your body such as glucose and amino acids as well as waste products that need to be removed from the body. Blood cells, proteins and Platelets are too large to enter Bowman;s capsule.
- Capillaries around the proximal tubule re absorb needed substances by diffusion. Other substances remain in the tubule.
- Sodium ions must be actively transported out of the tubules. They are pumped back into the capillaries.
- Negative ions such as chloride follow the sodium and combine to form salts. These salts draw water from the tubules to be reabsorbed by the capillaries.
- 20mL of the original 120mL remains in the tubule and of this 20mL, 19mL can be kept or lost depending on the body's need for water. This is controlled by the hormone ADH (antidiaretic hormone)
- The reabsorbed substances, needed by the body, are returned to the veins and enter the circulatory system. The wastes, dissolved in small amounts of water, remain in the tubule and form urine. Urine produced by the nephrons enters the collecting tubules which eventualy reaches the bladder.
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