Copyright o The McGraw-Hill Companies, Inc. Per mission required for reproduction or display. TABLE 12-1 The Cardiovascular System COMPONENT FUNCTION Hear Atria Chambers through which blood flows from veins to ventricles. Atrial contraction adds to ventricular filling but is not essential for it Ventricles Chambers whose contractions produce the pressures that drive blood through the pulmonary and systemi vascular systems and back to the heart Vascular system Arteries Low-resistance tubes conducting blood to the various organs with little loss in pressure. They also act as pressure reservoirs for maintaining blood flow during ventricular relaxation Arterioles Major sites of resistance to flow, responsible for the pattern of blood flow distribution to the various organs; participate in the regulation of arterial blood pressure Capillaries Sites of nutrient, metabolic end product, and fluid exchange between blood and tissues. Venules ites of nutrient, metabolic end product, and fluid exchange between blood and tissues Low-resistance conduits for blood flow back to the heart their capacity for blood is adjusted to facilitate this flow Blood Plasma Liquid portion of blood that contains dissolved nutrients, ions, wastes, gases, and other substances. Its composition equilibrates with that of interstitial fluid at the capillaries Cells Includes erythrocytes that function mainly in gas transport, leukocytes that function in immune defenses, and platelets(cell fragments) for blood clotting