Let's start by discussing the structure of our blood vessels. Let's each take a characteristic of (1) arteries, (2) veins, or (3) capillaries. Build upon what your classmates say to enable us to have a fuller understanding of these vessels that are essential for our existence. Cardiac output is the amount of blood ejected from the left or right ventricle in any given minute. Cardiac output must be maintained in order to keep sufficient blood flow through the capillaries. Identify and describe the factors that directly affect blood flow in the circulatory system.