Complex urban water systems seem rather simple when compared to the intricacy and coordinated functions of blood vessels. The heart is the pump that provides the major force causing blood to circulate, and the blood vessels are the pipes that carry blood to tissues of the body and back to the heart. In addition, the blood vessels participate in the regulation of blood pressure and help direct blood flow to tissues that are most active.

The peripheral circulatory system comprises two sets of blood vessels: systemic and pulmonary vessels. Systemic vessels transport blood through essentially all parts of the body from the left ventricle and back to the right atrium. Pulmonary vessels transport blood from the right ventricle through the lungs and back to the left atrium (see figure 20.1). Both the blood vessels and the heart are regulated to ensure that the blood pressure is high enough to cause blood flow in sufficient quantities to meet the metabolic needs of the tissues. The cardiovascular system ensures the survival of the tissues in the body by supplying nutrients to and removing waste products from them.

This chapter explains the functions of the peripheral circulation (p. 724) general features of blood vessel structure (p. 724), pulmonary circulation (p. 730), systemic circulation: arteries (p. 730), systemic circulation: veins (p. 741), dynamics of blood circulation (p. 753), physiology of systemic circulation (p. 757), control of blood flowin tissues (p. 762), and regulation of mean arterial pressure (p. 766).