Starling's hypothesis

Starling's Hypothesis is a physiological principle that describes the regulation of fluid exchange across the capillary walls in the circulatory system. It was proposed by the British physiologist Ernest Starling in 1896.

Overview

Starling's Hypothesis states that the fluid movement across the capillary wall is determined by the balance between hydrostatic pressure and osmotic pressure. The hydrostatic pressure tends to push fluid out of the capillary, while the osmotic pressure tends to pull fluid back into the capillary. The net fluid movement is the difference between these two pressures.

Hydrostatic Pressure

Hydrostatic pressure is the pressure exerted by a fluid at equilibrium due to the force of gravity. In the context of Starling's Hypothesis, it refers to the blood pressure within the capillaries. This pressure is highest at the arteriolar end of the capillary and lowest at the venular end, which promotes the movement of fluid out of the capillary and into the interstitial space.

Osmotic Pressure

Osmotic pressure is the pressure required to prevent the flow of water across a semipermeable membrane via osmosis. In the circulatory system, this pressure is primarily generated by plasma proteins, particularly albumin, which are too large to cross the capillary wall. These proteins exert a pulling force that draws water back into the capillary.

Clinical Significance

Understanding Starling's Hypothesis is crucial in the clinical setting, particularly in the management of conditions such as edema, heart failure, and kidney disease. For example, in heart failure, the hydrostatic pressure in the capillaries may be abnormally high, leading to excessive fluid leakage into the interstitial space and resulting in edema.

See Also

• Capillary
• Hydrostatic pressure
• Osmotic pressure
• Edema
• Heart failure
• Kidney disease

References

• Starling EH. On the Absorption of Fluids from the Connective Tissue Spaces. J Physiol. 1896;19(4):312-326.

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