<prompt> Which of the following is not true about Laplace Law?TPrWP2TrPTrPTw  <response>: 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 Prw 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 T1r1 1r2 In a sphere, r1 r2, so P2Tr In a cylinder such as a blood vessel, one radius is infinite, so P Tr Ref: Ganongs 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 moreincreased 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. 