Closed and Open Circulatory Systems

1. Closed and Open Circulatory Systems Closed system: Blood never leaves vessels. Blood travels through closed blood vessels Lymph travels through closed lymph vessels Single heart

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

3. The Human Heart Pulmonary circulation Aorta 1. Blood returns to heart from body, enters right atrium. Superior vena cava Pulmonary artery 6 3 2. Blood enters right ventricle. Pulmonary vein 3. Blood is pumped from right ventricle to lungs. 4 Right atrium Left atrium 1 Systemic circulation Atrioventricular valve Atrioventricular valve 4. Blood returns to left atrium from lungs. Semilunar valves 5 5. Blood enters left ventricle. 2 Inferior vena cava 6. Blood is pumped from left ventricle to body. Left ventricle Right ventricle

4. Partial Pressures of Gases Vary throughout the Human Circulatory System Tissues PO240 mm Hg PCO245 mm Hg Blood leaving tissue capillaries PO2 40 mm Hg PCO2 45 mm Hg Blood entering tissue capillaries PO2 140 mm Hg PCO2 40 mm Hg Systemic circulation Inhaled air PO2 160 mm Hg PCO2 0.3 mm Hg Exhaled air PO2 120 mm Hg PCO2 27 mm Hg Pulmonary artery Pulmonary vein Aorta Pulmonary circulation Venae cavae Blood leaving alveolar capillaries PO2 104 mm Hg PCO2 40 mm Hg Blood entering alveolar capillaries PO2 40 mm Hg PCO2 45 mm Hg Alveoli of lungs PO2 104 mm Hg PCO2 40 mm Hg

5. Blood Pressure Changes during the Cardiac Cycle Cardiac cycle Ventricular systole Ventricular diastole Systolic blood pressure Aortic valve opens Aortic pressure Diastolic blood pressure Aortic valves closes Ventricular pressure Atrioventricular valves close Atrioventricular valves open Atrial pressure

6. EKGs Record Electrical Events Associated with Cardiac Muscle Contraction SA node activates atria AV node delay Ventricles recover Electrical activity in ventricles Electrical activity in atria

7. 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.

8. Blood Pressure Drops Dramatically in the Circulatory System From heart Capillaries Return to heart Velocity Total area

9. 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.