Human Physiology Essay Example | Topics and Well Written Essays - 500 words

Human Physiology - Essay Example Resistance to flow through a vessel is also inversely related to its radius raised to the fourth power. Even a small decrease in the radius of the vessel would result in a large increase in the resistance to flow. At any given point in time the most important factors governing the smooth functioning of the blood circulatory system are volume, pressure, resistance and flow. For the optimal functioning of the system it requires a specific and a pressure that is necessary and sufficient to ensure the flow of blood through all body tissues. The relation between pressure (P), resistance (R) and blood flow (F) is given by the equation, F = P/R. P precisely is the difference in pressure between the two ends of the system. In pulmonary circulation the total resistance is approximated at 0.12 PRU. In this case, the flow of blood is the same as systemic circulation. However the pressure difference between the two ends of the system is much less. According to Poiseuilli, a French physician, flow of blood is also affected by viscosity of blood. It explains the resistance to flow due to the friction caused by the molecules present in the blood. Blood being a non-homogenous fluid, more number of molecules is present resulting in greater friction and hence increased resistance to flow. Porth C.