Cardiovascular System The Heart

The Cardiovascular System A closed system of the heart and blood vessels The heart pumps blood Blood vessels allow blood to circulate to all parts of the body The function of the cardiovascular system is to deliver oxygen and nutrients and to remove carbon dioxide and other waste products

Systemic Circulation – delivers blood to all body cells and carries away waste Pulmonary Circulation – eliminates carbon dioxide and oxygenates blood (lung pathway)

The distal end of the heart is called the apex. Structure of the Heart About the size of a fist. Located in the mediastinum (space between lungs, backbone, sternum), between the 2nd rib and the 5th intercostal space. The distal end of the heart is called the apex.

Protective Coverings of the Heart Fibrous Pericardium encloses the heart and has 2 layers Visceral pericardium (inner) Parietal pericardium (outer, attached to diaphragm, sternum and vertebrae) Pericardial cavity contains fluid for the heart to float in and reduces friction

Wall of the Heart Epicardium – outer layer, reduces friction Myocardium – middle layer, mostly cardiac muscle Endocardium – thin inner lining, within chambers of the heart

Heart Chambers & Valves Your heart is a double pump. Circulation is a double circuit: Pulmonary (lungs only) and systemic (rest of the body) Heart has 4 chambers: 2 Atria – thin upper chambers that receive blood returning to the heart through veins. Right and Left 2 Ventricles – thick, muscular lower chambers. Receive blood from the atria above them. Force (pump) blood out of the heart through arteries. Right and left Septum – separates the right and left sides of the heart

Valves of the Heart Allow one-way flow of blood 4 total—2 Atrioventricular Valves (AV) & 2 Semilunar valves Left Atrioventricular valve – also called the bicuspid valve or mitral valve. Between left atrium and ventricle Right Atrioventricular valve – also called the tricuspid valve. Between right atrium and ventricle Aortic Semilunar – or just aortic valve. Between the left ventricle and the aorta Pulmonary Semilunar, or just pulmonary valve. Between the right ventricle and the pulmonary trunk

The cusps (flaps) of the bicuspid and tricuspid valves are anchored to the ventricle walls by fibrous “cords” called chordae tendineae, which attach to the wall by papillary muscles. This prevents the valves from being pushed up into the atria during ventricular systole.

Mitral = bicuspid (left side) Tricuspid (right side) Aortic and Pulmonary are both semilunar valves

Blood Flow Through the Heart Blood that is low in oxygen and high in CO2 enters right atrium through the superior and inferior vena cavae From (contraction) right atrium, through the tricuspid valve, blood travels to the right ventricle From (contraction) the right ventricle, blood leaves the heart as it passes through the pulmonary semilunar valve into the pulmonary trunk Pulmonary trunk splits into right and left pulmonary arteries that carry blood to the lungs

Blood Flow Through the Heart 5. Oxygen is picked up and carbon dioxide is dropped off by blood in the lungs 6. Oxygen-rich blood returns to the heart through the four pulmonary veins 7. Blood enters the left atrium and travels through the bicuspid (mitral) valve into the left ventricle 8. From the left ventricle, (wall contracts) blood leaves the heart via the aortic semilunar valve and aorta 9. Oxygenated blood flows to all body tissues

Path of Blood Flow

Heart Contractions Contraction is initiated by the sinoatrial node (SA node) Sequential stimulation occurs at other autorhythmic cells, forcing cardiac muscle depolarization in one direction—from atria to ventricles Once SA node starts the heartbeat Impulse spreads to the AV node Then the atria contract At the AV node, the impulse passes through the AV bundle, bundle branches, and Purkinje fibers Blood is ejected from the ventricles to the aorta and pulmonary trunk as the ventricles contract

1. Sinoatrial node (Pacemaker) 2. Atrioventricular node 3 1. Sinoatrial node (Pacemaker) 2. Atrioventricular node 3. Atrioventricular Bundle (Bundle of His) 4. Left & Right Bundle branches 5. Bundle Branches (Purkinje Fibers)