BRAINCAKETissue Fluid
Every cell in the body is surrounded and bathed by a liquid called tissue fluid. Cells are not in direct contact with the blood, so all exchange of substances between the blood and cells takes place through the tissue fluid.
Tissue fluid is formed from blood plasma that is pushed out of the capillaries through the small gaps between the endothelial cells. It therefore contains many of the same substances as plasma, including water, glucose, amino acids, fatty acids, ions and oxygen. However, it contains no red blood cells and very few plasma proteins, because these are too large to pass through the capillary wall. A few white blood cells can squeeze out into the tissue fluid to fight infection.
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Key terms in this lesson
- oncotic pressure
- The pressure created by plasma proteins, which are too large to leave the capillaries, that draws water back into the capillaries by osmosis.
- hydrostatic pressure
- The pressure a fluid exerts on the walls of its container; in a capillary it pushes fluid out through the gaps between the endothelial cells.
More in Circulatory Systems
- Arteries
- Arterioles
- Capillaries
- Veins and venules
- Oncotic Pressure
- Hydrostatic Pressure
- Arterial End of Capillaries
- Venous End of Capillaries
All 33 lessons in Circulatory Systems · All Edexcel AS-level Biology topics