The maintenance of normal pressures within the arterial and venous circulations is essential for the maintenance of normal fluid homeostasis. The '''Starling hypothesis''' describes the state whereby the equilibrium of fluid exchange across the capillary wall (between the blood and the interstitial fluid) is determined by the hydrostatic pressures and oncotic pressures that exist across the capillary wall. This fluid exchange is controlled by the capillary blood pressure, the interstitial fluid pressure and the colloid osmotic pressure of the plasma. Normally there is a net loss of fluid from the capillary at the arteriolar end, and a net gain at the venous end, resulting in almost perfect fluid balance being maintained. Any net fluid movement from the intravascular to the extracellular space can be compensated for by lymphatic drainage. Low blood pressure results in fluid moving from the interstitial space into the circulation, helping to restore blood volume and blood pressure. | The maintenance of normal pressures within the arterial and venous circulations is essential for the maintenance of normal fluid homeostasis. The '''Starling hypothesis''' describes the state whereby the equilibrium of fluid exchange across the capillary wall (between the blood and the interstitial fluid) is determined by the hydrostatic pressures and oncotic pressures that exist across the capillary wall. This fluid exchange is controlled by the capillary blood pressure, the interstitial fluid pressure and the colloid osmotic pressure of the plasma. Normally there is a net loss of fluid from the capillary at the arteriolar end, and a net gain at the venous end, resulting in almost perfect fluid balance being maintained. Any net fluid movement from the intravascular to the extracellular space can be compensated for by lymphatic drainage. Low blood pressure results in fluid moving from the interstitial space into the circulation, helping to restore blood volume and blood pressure. |