Plasma constitutes 55% of total blood fluid, and is 90% water. The other 10% of
substances, dissolved in plasma, are mostly proteins. These dissolved substances
are circulated throughout the body, and diffuse from areas of high concentration,
to areas of lower concentration, into tissues and cells. Waste materials flow in
the opposite direction, where they are removed by the kidneys or lungs. There are
approximately 2.7 – 3 litres of plasma in an average adult.
- Transports platelets and blood cells
- Contains a few hours of reserve protein.
- Carries drugs to site of action.
- Viscous - so resists blood flow.
- Contains high molecular weight substances, creating high osmotic pressure.
- Draws fluid into blood vessels, preventing oedema.