define blood flow, blood pressure and resistance and explain the relationships between these factors
Resistance - is opposition to flow and is a measure of the amount of friction blood encounters as it passes through the vessels. Blood flow (F) is directly proportional to the difference in blood pressure (Î´P) between two points in the circulation, that is, the blood pressure, or hydrostatic pressure, gradient. Thus, when Î´P increases, blood flow speeds up, and when Î´P decreases, blood flow declines.
R = Î´ P Q {\displaystyle R={\frac {\Delta P}{Q}}}. where R is the pulmonary vascular resistance (fluid resistance), Î´P is the pressure difference across the pulmonary circuit, and Q is the rate of blood flow through it.