Functions Transport system nutrients from digested food all body cells oxygen from the lungs all body cells metabolic wastes (CO 2 ) organs to be excreted hormones target tissues Regulates body temperature in a warm environment blood vessels dilate, allowing more heat to leave the body in a cold environment blood vessels constrict, preventing heat from escaping from the body Arteries carry oxygenated blood away from the heart arterioles small arteries thick elastic walls to withstand the pumping action of the heart high blood pressure Capillaries connect arterioles to venules Walls are only one cell thick so molecules can easily diffuse across Nutrients diffuse from capillaries body cells Wastes diffuse from body cells capillaries Capillaries are vey narrow; thickness of a single RBC Veins carry deoxygenated blood back to the heart thin walls due to low blood pressure have valves to help prevent backflow of blood A muscular pump that propels blood through the blood vessels Atria two upper chambers that receive blood returning to the heart Ventricles two lower thickwalled chambers that pump blood away from the heart Pericardium protective sac around the heart Vena cava largest veins Superior drains blood from the upper body into right atrium Inferior drains blood from the lower body into right atrium Aorta largest artery comes from left ventricle and branches to deliver blood to the entire body Pulmonary arteries carry blood from the heart to the lungs Pulmonary veins carry blood from the lungs back to the heart Coronary arteries delivers blood to cardiac muscle When the coronary arteries become blocked a heart attack occurs Stroke when blood supply is cut off to the brain and an area of the brain dies. Valves prevent the backflow of blood as it is being pumped through the heart Named according to where they lead or how they look Atrioventricular Valves between the atria and ventricles tRicuspid on the Right side bicuspid on the left side (a.k.a. as the mitral v.) Semilunar Valves between the ventricles and arteries pulmonary right ventricle pulmonary artery aortic left ventricle aorta Vena cava right atrium tricuspid valve right ventricle pulmonary valve pulmonary artery lungs pulmonary veins left atrium bicuspid valve left ventricle aortic valve aorta The left side of the heart pumps oxygenrich blood out to the body through a network of arteries Oxygenpoor blood is returned to the right side of the heart through veins. The right side of the heart pumps oxygen poor blood through the pulmonary arteries to the lungs. Gas exchange (release of C0 2 and and pick up of O 2 ) occurs in the lungs. The oxygenrich blood then returns to the left side of the heart through pulmonary veins In the pulmonary circuit the oxygen content of the vessels is reversed! The pulmonary artery carries oxygenpoor blood away from the heart to the lungs The pulmonary vein carries oxygenrich blood from the lungs back to the heart Sinoatrial (SA) node acts as the pacemaker for the heart cluster of cells located in the upper wall of the right atrium sends a rhythmic electrical stimulus causing both atria to contract pushing blood into the ventricles Atrioventricular (AV) node in between the atria causes contraction of the ventricles just after the atria contract pushing blood out of the heart