Engineer's Model of the Cardiovascular System
The cardiovascular system can be viewed as a two circuit (pulmonary and systemic), closed irrigation system with blood being propelled by a two phase pump (the heart). One way flow both to and from the lungs and tissues is controlled by valves. Oxygen (red) is taken up by the capillaries in the lungs and delivered to cells by tissue microvessels. The primary plumping of this system is the larger vessels usually categorized by their cross sectional diameter (caliber) and the properties of the tunics (layers) in their walls. Portal systems (capillary beds found between veins) are involved in blood processing before return to the heart. Microvessels (capillaries and venules) constitute the exchange vessels where gases and nutrients are exchanged with the tisse cells.