Resistance to blood flow or vascular resistance refers to the slow down of the blood flow due to friction between the flowing blood and the walls of the blood vessels.
The resistance to blood flow is regulated by the viscosity of blood, total length, and diameter of the blood vessels. Higher blood viscosity imparts more resistance to the blood flow. The reduced diameter of blood vessels also restricts the blood flow through the blood vessels. Similarly, the resistance to the blood flow is directly proportional to the total length of the blood vessels.
However, total blood volume present in the body of the organisms does not affect vascular resistance. The total blood volume affects the blood pressure which in turn would affect the systemic vascular resistance.
For a quantity of water, milliliters (mL) are used For the length of a leaf centimeters or millimeters (cm; mm) are used For the mass of a small stone, gram (g) are used.
