Objectives • Describe the functional organization of cardiovascular system • List the functions of cardiovascular system. • Describe the main function of arteries, capillaries and veins • Describe the flow of blood through the chambers of the heart and through the systemic and pulmonary circulations. • Compare and contrast the systemic and pulmonary circulation.
HEART (PUMP) CARDIOVASCULAR SYSTEM VESSELS (DISTRIBUTION SYSTEM) Blood Functional Organization of Cardiovascular system
Functions of Cardiovascular System: I. Primary (main) function of the heart: ♥ Acts as a muscular pump: in order to maintain adequate level of blood flow throughout CVS by pumping blood under press into vascular system. ♥ Responsible for the mass movement of fluid in body.
Functions of Cardiovascular System (continued) II. Secondary functions: 1. Transportation: delivers O2 to tissues, & brings back CO2 to lungs. carries absorbed digestion products to liver & tissues. carries metabolic wastes to kidneys to be excreted. distribution of body fluids. 2. Regulation: Hormonal: carries hormones to target tissues to produce their effects. Immune: carries antibodies, leukocytes (WBCs), cytokines, & complement to aid body defense mechanism against pathogens. Protection: carries platelets, & clotting factors to aid protection of the body in blood clotting mechanism. Temperature: helps in regulation of body temperature, by diverting blood to cool or warm the body.
Anatomy of the heart: • Positioned between two bony structures – sternum and vertebrae (CPR) • Hollow, muscular organ.
Vena cava pulmonary veins Pulmonary trunk (Aorta)
Atrium: weak primer pump for the ventricle Ventricle: the main pumping force Rt. Ventricle Lt. ventricle Pulmonary circulation Systemic circulation
systemic circulation Pulmonary circulation
Valves of the heart: ♥2 atrioventricular (AV) valves: ■One way valves. ■Allow blood to flow from atria into ventricles. ■ Tricuspid (Rt) & Mitral (Lt). ♥2 semilunar valves: ■One way valves. ■At origin of pulmonary artery & aorta. ■ Pulmonary (Rt) & Aortic (Lt). ■ Open during ventricular contraction.
Heart Valves • One way flow in heart is ensured by heart valves • Valves open & close passively - open by forward P by blood - close by backward P by blood
No valves between atria and veins • Reasons • Atrial pressures usually are not much higher than venous pressures • Sites where venae cavae enter atria are partially compressed during atrial contraction
Serves 3 roles: A mechanical base: atria anchored above and ventricles below Perforated by 4 apertures, each containing a valve Insulates the ventricles The fibrous skeleton of the heart
Vascular Tree • Closed system of vessels • Consists of • Arteries • Carry blood away from heart to tissues • Arterioles • Smaller branches of arteries • Capillaries • Smaller branches of arterioles • Smallest of vessels across which all exchanges are made with surrounding cells • Venules • Formed when capillaries rejoin • Return blood to heart • Veins • Formed when venules merge • Return blood to heart
Arteries • Function: • Rapid transit passage-ways for blood from heart to tissues • Pressure reservoir Structure of arterial wall • Plentiful of elastic fibers….high compliance
Arterioles (resistance vessels) • Very small arteries that delivers blood to capillaries • Structure • Very little elastic tissue but thick layer of smooth muscle • Function Regulating blood flow from arteries to capillaries by regulating resistance according to tissue metabolic needs.
Capillaries • Microscopic vessels that connects arterioles to venules • Structure • Single wall layered vessels (endothelial cells) • Undergoes extensive branching • Maximized surface area and minimized diffusion distance • Velocity of blood flow through capillaries is relatively slow • Provides adequate exchange time • Function: • Exchange of nutrients and wastes between blood and tissue cells
Capillaries cont. • Under resting conditions many capillaries are not open • Capillaries surrounded by precapillary sphincters • Contraction of sphincters reduces blood flowing into capillaries in an organ • Relaxation of sphincters has opposite effect
Veins • Carry blood from tissues to heart • Structure: • Thin wall • Less smooth muscle and considerable amount of collagen • Less elastic fibers • Function: • Passage ways back to heart • Blood reservoir (capacitance vessels)