Which of the following is not true about “Laplace Law”?
Correct Answer: P=T/w
Description: This law states that tension in the wall of a cylinder (T) is equal to the product of the transmural pressure (P) and the radius (r) divided by the wall thickness (w): T = Pr/w In a thin-walled viscus, w is very small and it too can be ignored, but it becomes a significant factor in vessels such as aeries. Therefore, in a thin-walled viscus, P = T divided by the two principal radii of curvature of the viscus: P = T(1/r1 + 1/r2) In a sphere, r1 = r2, so P=2T/r In a cylinder such as a blood vessel, one radius is infinite, so P = T/r Ref: Ganong's Review of medical physiology 25th edition. Page:574 This law helps to understand the physiological nechanisms in altered situations and pathological conditions . Eg: in hollow organs like bladder,ventricle,or alveoli of lungs the wall tension increases when the organ gets fillled ie P rises or the cavity size (R) increases. In ventricular hyperophy, the wall is thick so,wall tension is less. In dialated hea as in hea failure, more energy is required to pump blood as the wall tension is more(increased R) . So dialated hea pumos blood less effitiently Capillaries are less prone to rupture because smaller the radius lesser the tension in tha wall needed to balance the distending pressure.
Category:
Physiology
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