Chapter 18 The Cardiovascular System The Heart Heart Anatomy The heart is no more than the transport system pump and the hollow blood vessels are the delivery routes The blood acts as the transport medium The heart propels oxygen nutrients wastes and other substances into the interconnecting blood vessels that service body cells 1 Describe the size location and orientation of the heart About the size of a fist Hollow cone shaped Mass between 250 350 grams less than a lb Enclosed within mediastinum the medial cavity of thorax Heart extends about 5 inches from second rib to fifth intercostal space Posterior surface or broad flat base 9cm 3 5 inches Apex Apical impulse points interiorly toward hip caused by apex of beating heart contracting against chest wall 2 Identify structures of the pericardium Pericardium double walled sac membrane that encloses the heart o Fibrous pericardium Loose fitting superficial part of sac Protects heart Anchors it to surrounding area Prevents overfilling of the heart with blood o Serous pericardium under fibrous pericardium Thin slippery two layer serous membrane Has a parietal layer which lines the internal surface of the fibrous pericardium This layer also attatches to large arteries exiting heart then turns and continues over the external heart surface as the visceral layer epicardium which is an integral part of heart wall Between parietal and visceral layers Contains a film of serous fluis The serous membrance are lubricated by the fluid and glide easily past one another during heart activity allowing the mobile heart to work in a relativery friction free environment o Pericardial cavity 3 Define the endocardium myocardium and epicardium Layers if the heart wall are richly supplied with blood vessels Composed of three layers epicardium myocardium and endocardium Epicardium o superficial visceral layer of serous pericardium o Often infiltrated with fat mostly in older people Myocardium o Middle layer composed of cardial muscle and forms bulk of heart o The layer that contracts o Cardiac muscle cells are arranged in spiral or circular bundles that link all o Fibrous skeleton of the heart parts of the heart together the connective tissue fibers form a dense network that reinforces the myocardium internally and anchors cardiac muscle fibers Endocardium tissue o inside heart o glistening white sheet of endothelium resting on a thin layer of connective o lines heart chambers and covers the fibroud skeleton of the valves 4 Compare the function of the atria and the ventricles and describe the difference between the function of the right and left ventricles The heart has 4 chambers 2 superior atria and 2 inferior ventracles Interatrial septum seperates the atria internal partition that divides the heart longitudinally where it Interventricular septum internal partition that divides the heart longitudinally where it seperates the ventracles Coronary sulcus atrioventricular groove encirles the junctiona of the atria and Anterior interventricular sulcus makes the anterior of the septum seperating the Posterior interventricular sulcus provides a similar landmark on the heats ventracles like a crown right and left ventracles posterior surface Atria the receiving chambers o Auricles that increase atrial volume o Right atria has two basic parts called little ear are small wrinkled protruding appendages 1 Smooth walled posterior part 2 Anterior portion in which walls are ridged by bundles of muslce tissue They look like teeth of a comb and are called pectinate muscles o Posterior anterior regions of the heart are seperated by C Shaped ridge called crista terminalis o Left Atrium mostly smooth and pectinate muscles are only found in o Fossa ovalis shallow depresseion in interatrial septum that marks the auricle spot where an opening the foramen ovale existed in fetal heart circulation are the receiving chambers for blood returning to the heart from o Atria they are small and thin walled because they only contract minimally to push blood downstairs to the ventracles o blood enters the right atrium via 3 veins superior vena cava diaphragm inferior vena cava diaphragm coronary sinus returns blood from body regions superior the returns blood from body areas below o 4 pulmonary veins enter the left atrium which makes up most of the hearts collects blood draining from myocardium base these veins transport blood from lungs back to heart Ventracles the discharging chambers o Together they make up the volume of the heart o Trabeculae carneae ventricular chambers o Papillary muscles Conelike play a role in valve function project into ventricular cavity irregular ridges that mark the internal walls of the o Ventricles o When they contracstm blood is propelled out of the heart and into are the discharging chambers or actula pumps of the heart circulation o The right ventracle pumps blood into the pulmonary trunk which routes the blood to the lungs where gas exchange occurs o The left ventracle ejects blood into the aorta largest artery in body 5 Discuss the need for coronary circulation and name the vessels that play a role in it is the functional blood supply of the heart also the shortest Coronary circulation circulation in the body o The arterial supply if provided by left and right coronary arteries o Left coronary artery run toward left side of the heart and then divides into its major branches anterior interventricular artery septum and anterior walls of both ventracles circumflex artery ventracle supplies left atrium and posterior walls of left supplies blood to interventricular courses to the right side of the heart and has two o Right coronary artery Right marginal artery branches side of heart supplies the posterior ventricular walls Posterior interventricular artery that serves the myocardium of lateral right which runs to heart apex and o Anastomes junctions among coronary arterial branches These fusing networks provide additional collateral routes for blood delivery to heart muscle Not robust enough to supply the proper nutrition when an artery is A blockage leads to tissue death and heart attack blocked o Coronary Arteries Deliver blood when the heart is relaxed o Heart requires 1 20 of blood supply o Left ventracle recieves most plentiful blood supply o Cardiac veins vessel called coronary sinus empties blood into right atrium collect venous blood that join together to form enlarged o The sinus 3 large tributaries Great cardiac vein Middle cardiac vein Small
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