The Heart PDF

The Cardiovascular System: The Heart Anatomy Heart Anatomy Approximately the size of your fist Location Superior surface of diaphragm Left of the midline Anterior to the vertebral column, posterior to the sternum Heart Anatomy Coverings of the Heart: Anatomy Pericardium – a double-walled sac around...

The Cardiovascular System: The Heart Anatomy Heart Anatomy Approximately the size of your fist Location Superior surface of diaphragm Left of the midline Anterior to the vertebral column, posterior to the sternum Heart Anatomy Coverings of the Heart: Anatomy Pericardium – a double-walled sac around the heart composed of: 1. A superficial fibrous pericardium 2. A deep two-layer serous pericardium a. The parietal layer lines the internal surface of the fibrous pericardium b. The visceral layer or epicardium lines the surface of the heart c. They are separated by the fluid-filled pericardial cavity Coverings of the Heart: Physiology The Function of the Pericardium: Protects and anchors the heart Prevents overfilling of the heart with blood Allows for the heart to work in a relatively friction-free environment Heart Wall Epicardium – visceral layer of the serous pericardium Myocardium – cardiac muscle layer forming the bulk of the heart Fibrous skeleton of the heart – crisscrossing, interlacing layer of connective tissue Endocardium – endothelial layer of the inner myocardial surface Major External Vessels of the Heart Chapter 18, Cardiovascular System External Heart: Posterior View Pathway of Blood Through the Heart and Lungs Right atrium → tricuspid valve → right ventricle Right ventricle → pulmonary semilunar valve → pulmonary arteries → lungs Lungs → pulmonary veins → left atrium Left atrium → bicuspid valve → left ventricle Left ventricle → aortic semilunar valve → aorta Aorta → systemic circulation Pathway of Blood Through the Heart and Lungs; Pulmonary Circuit Figure 18.5 10 Major External Vessels of the Heart: Aortic Circulation Major External Vessels of the Heart: Aortic Circulation Major External Vessels of the Heart: Aortic Circulation, Celiac Trunk Major External Vessels of the Heart: Vertebral Artery/ Circle of Willis Coronary Circulation: Arterial Supply Coronary circulation is the functional blood supply to the heart muscle itself Collateral routes ensure blood delivery to heart even if major vessels are occluded Coronary Circulation: Arterial Supply Coronary Circulation: Venous Supply Venous drainage of the heart is mostly through the coronary sinus located on the posterior aspect of the heart Tributaries drain into the coronary sinus, which in turn, empties into the right atrium Coronary Circulation: Venous Supply Main tributaries Great cardiac vein ) Largest tributary Originates at the apex of the heart and ascends in the anterior interventricular groove Small cardiac vein Located on the anterior surface of the heart, between the right atrium and right ventricle Travels onto the posterior surface of the heart, where it empties into the coronary sinus Middle cardiac vein Begins at the apex of the heart and ascends in the posterior interventricular groove to empty into the coronary sinus Posterior cardiac vein Located on the posterior surface of the left ventricle Located left of the middle cardiac vein and empties into the coronary Chambers and Valves of the Heart Atria of the Heart Atria are the receiving chambers of the heart Each atrium has a protruding auricle Pectinate muscles mark atrial walls Blood enters right atria from superior and inferior venae cavae and coronary sinus Blood enters left atria from pulmonary veins Ventricles of the Heart Ventricles are the discharging chambers of the heart Papillary muscles and trabeculae carneae muscles mark ventricular walls Right ventricle pumps blood into the pulmonary trunk Left ventricle pumps blood into the aorta 21 Myocardial Thickness and Function Thickness of myocardium varies according to the function of the chamber Atria are thin walled, deliver blood to adjacent ventricles Ventricle walls are much thicker and stronger right ventricle supplies blood to the lungs (little flow resistance) left ventricle wall is the thickest to supply systemic circulation Thickness of Cardiac Walls Myocardium of left ventricle is much thicker than the right Heart Valves Heart valves ensure unidirectional blood flow through the heart Atrioventricular (AV) valves lie between the atria and the ventricles AV valves prevent backflow into the atria when ventricles contract Chordae tendineae anchor AV valves to papillary muscles Heart Valves Semilunar valves prevent backflow of blood into the ventricles Aortic semilunar valve lies between the left ventricle and the aorta Pulmonary semilunar valve lies between the right ventricle and pulmonary trunk Heart Valves Heart Valves Chapter 18, Cardiovascular System Figure 27 18.8c, d Atrioventricular Valve Function Semilunar Valve Function Mitral Valve Prolapse Microscopic Anatomy of Heart Muscle Cardiac muscle is striated, short, fat, branched, and interconnected The connective tissue endomysium acts as both tendon and insertion Intercalated discs anchor cardiac cells together and allow free passage of ions Heart muscle behaves as a functional syncytium