ANATOMY

Detailed explanation-1: -There are three primary factors that determine the resistance to blood flow within a single vessel: vessel diameter (or radius), vessel length, and viscosity of the blood. Of these three factors, the most important quantitatively and physiologically is vessel diameter.

Detailed explanation-2: -The three most important factors affecting resistance are blood viscosity, vessel length and vessel diameter and are each considered below.

Detailed explanation-3: -You need to know the factors that affect blood flow through the cardiovascular system: blood pressure, blood volume, resistance, disease and exercise.

Detailed explanation-4: -Although SVR is primarily determined by changes in blood vessel diameters, changes in blood viscosity also affect SVR. SVR can be calculated if cardiac output (CO), mean arterial pressure (MAP), and central venous pressure (CVP) are known.

Detailed explanation-5: -It has long been known that increased blood viscosity increases systemic vascular resistance and, secondarily, decreases total cardiac output in the intact circulation.