Biology – The circulatory system | e-Consult
The circulatory system (1 questions)
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Tissue fluid, also known as interstitial fluid, is formed from plasma that has passed out of the capillaries. The process occurs due to differences in hydrostatic and osmotic pressures across the capillary walls.
Formation Process:
- Hydrostatic Pressure (HP): Blood pressure within the capillaries pushes water and small solutes out of the capillaries and into the surrounding interstitial space. This is the driving force for filtration.
- Colloid Osmotic Pressure (COP): Plasma proteins remain within the capillaries due to their large size, creating an osmotic pressure that draws water back into the capillaries. This opposes filtration.
- Net Filtration Pressure (NFP): The NFP is the difference between HP and COP. It determines the rate and direction of fluid movement. A positive NFP indicates filtration, while a negative NFP indicates reabsorption.
Factors Influencing the Rate of Filtration:
- Hydrostatic Pressure (HP): An increase in blood pressure will increase the hydrostatic pressure, leading to a higher rate of filtration. Conversely, a decrease in blood pressure will decrease filtration.
- Colloid Osmotic Pressure (COP): An increase in plasma protein concentration will increase the COP, leading to a lower rate of filtration. A decrease in plasma protein concentration will decrease filtration.
- Capillary Hydrostatic Pressure: Changes in capillary diameter can affect HP. Vasodilation decreases HP, reducing filtration. Vasoconstriction increases HP, increasing filtration.
- Capillary Permeability: The permeability of the capillary walls can influence the rate of filtration. Increased permeability allows for more fluid to pass through.
The net filtration pressure is crucial for maintaining fluid balance in the tissues.