Copyright © 2008 Pearson Education Inc., publishing as Pearson Addison-Wesley Closed and Open Circulatory Systems Closed system: Blood never leaves vessels. Blood travels through closed blood vessels Single heart Lymph travels through closed lymph vessels

Copyright © 2008 Pearson Education Inc., publishing as Pearson Addison-Wesley The Evolution of the Vertebrate Circulatory System Fish Two circulatory loops 1 circuit 2-chambered heart Frogs Gills Lung Turtles, lizards 2 circuits 3-chambered heart Lung 2 circuits “5-chambered” heart Crocodiles Lung 2 circuits 4-chambered heart Birds Lung 2 circuits 4-chambered heart Mammals Lung 2 circuits 4-chambered heart Body Three-chambered heart Ventricle divided into chambers A  Atrium V  Ventricle A V A V A A V A A V A V A V A V A V A V

Copyright © 2008 Pearson Education Inc., publishing as Pearson Addison-Wesley The Human Heart Aorta Pulmonary artery Pulmonary vein Left atrium Semilunar valves Atrioventricular valve Left ventricle Right atrium Atrioventricular valve Right ventricle Inferior vena cava Superior vena cava 6 Pulmonary circulation Blood returns to heart from body, enters right atrium. Blood is pumped from right ventricle to lungs. Blood enters right ventricle. Systemic circulation Blood is pumped from left ventricle to body. Blood returns to left atrium from lungs. Blood enters left ventricle

Copyright © 2008 Pearson Education Inc., publishing as Pearson Addison-Wesley Partial Pressures of Gases Vary throughout the Human Circulatory System Pulmonary circulation Systemic circulation Venae cavae Pulmonary artery Aorta Blood leaving tissue capillaries P O 2 40 mm Hg P CO 2 45 mm Hg Pulmonary vein Tissues P O 2  40 mm Hg P CO 2  45 mm Hg Blood entering tissue capillaries P O mm Hg P CO 2 40 mm Hg Inhaled air P O mm Hg P CO mm Hg Exhaled air P O mm Hg P CO 2 27 mm Hg Blood entering alveolar capillaries P O 2 40 mm Hg P CO 2 45 mm Hg Blood leaving alveolar capillaries P O mm Hg P CO 2 40 mm Hg Alveoli of lungs P O mm Hg P CO 2 40 mm Hg

Copyright © 2008 Pearson Education Inc., publishing as Pearson Addison-Wesley Blood Pressure Changes during the Cardiac Cycle Systolic blood pressure Diastolic blood pressure Ventricular pressure Atrial pressure Atrioventricular valves open Aortic pressure Aortic valves closes Atrioventricular valves close Aortic valve opens Ventricular systoleVentricular diastole Cardiac cycle

Copyright © 2008 Pearson Education Inc., publishing as Pearson Addison-Wesley EKGs Record Electrical Events Associated with Cardiac Muscle Contraction SA node activates atria AV node delay Electrical activity in atria Electrical activity in ventricles Ventricles recover

Copyright © 2008 Pearson Education Inc., publishing as Pearson Addison-Wesley Patterns in Blood Pressure and Blood Flow Blood pressure is the force that blood exerts on the walls of arteries, capillaries, and veins. Blood pressure drops dramatically as blood moves through the capillaries, because the total cross-sectional area of blood vessels in the circulatory system increases greatly. The drop in blood pressure decreases the rate of blood flow to allow sufficient time for gases, nutrients, and wastes to diffuse between tissues and blood in the capillaries. Falling blood pressure is detected by baroreceptors in the walls of the heart and the major arteries.

Copyright © 2008 Pearson Education Inc., publishing as Pearson Addison-Wesley Blood Pressure Drops Dramatically in the Circulatory System From heartCapillariesReturn to heart Velocity Total area

Copyright © 2008 Pearson Education Inc., publishing as Pearson Addison-Wesley Patterns in Blood Pressure and Blood Flow When baroreceptors detect a major decrease in blood pressure, they trigger electrical signals that change the heart’s output and vessel diameter: (1)Cardiac output is increased by an increase in both heart rate and the amount of blood pushed out by the ventricles. (2)Arterioles serving the capillaries of noncritical tissues such as the skin and intestines are constricted to divert blood to more critical organs. (3)The veins are constricted, shifting blood volume toward the heart and arteries to maintain blood pressure and flow to vital organs.