Formation of Urine
- Created by: Tripat
- Created on: 30-10-12 18:35
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- Formation of Urine
- Ultrafiltration
- Urea, along with salt, water and glucose, etc., is extracted from the blood in the kidney in this process
- Blood passing the top of the nephron is under high pressure, so fluid is forced through the sieve-like capillaries and into the capsule.
- This fluid is called the filtrate.
- Much of what has been filtered out needs to be returned to the blood in a process is called selective reabsorption.
- Selective Reabsorption
- When the filtrate reaches the proximal convoluted tubule, sodium (Na+) and chloride (Cl?) ions, glucose, amino acids and vitamins move back into the blood.
- They are then actively transported out of these cells and into the blood capillaries.
- Some water follows by osmosis. Surprisingly, some unwanted urea also gets reabsorbed here.
- Ultrafiltration
- It does not contain any blood cells or larger proteins, as they are too big to pass out of the capillaries and into the capsule.
- This fluid is called the filtrate.
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