The Circulatory System Circulatory System or cardiovascular system, in humans, is the combined function of the heart, blood, and blood vessels to transport oxygen and nutrients to organs and tissues throughout the body and carry away waste products (Encarta 2000). The heart, blood, and blood vessels are the three structural elements that make up the circulatory system. The Heart: The heart is the engine or the pump of the circulatory system. It is divided into four …showed first 75 words of 816 total…

…showed last 75 words of 816 total…a number of factors, such as the contraction of the heart, the elasticity of arterial walls, blood volume, and resistance of blood vessels to the passage of blood. Blood pressure is the ratio between the Systolic (When heart pumps the blood) and diastolic (when the heart is resting) pressures of the blood (Encarta 2000). It is measured in units of millimeters of mercury (abbreviated mm Hg) and the average normal blood pressure is about 120/80 mm Hg.