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BIOB32H3 (80)
Lecture

The Cardiovascular System.docx

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Department
Biological Sciences
Course
BIOB32H3
Professor
Kenneth Welch
Semester
Fall

Description
The Cardiovascular System: The Heart 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 Covering • Pericardial physiology • Protects and anchors heart • Prevents overfilling Heart Covering • Pericardial anatomy • Fibrous pericardium • Serous pericardium (separated by pericardial cavity) • Epicardium (visceral layer) 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 External Heart: Major Vessels of the Heart (Anterior View) • Returning blood to the heart • Superior and inferior venae cavae • Right and left pulmonary veins • Conveying blood away from the heart • Pulmonary trunk, which splits into right and left pulmonary arteries • Ascending aorta (three branches) – brachiocephalic, left common carotid, and subclavian arteries External Heart: Vessels that Supply/Drain the Heart (Anterior View) • Arteries – right and left coronary (in atrioventricular groove), marginal, circumflex, and anterior interventricular • Veins – small cardiac vein, anterior cardiac vein, and great cardiac vein External Heart: Major Vessels of the Heart (Posterior View) • Returning blood to the heart • Right and left pulmonary veins • Superior and inferior venae cavae • Conveying blood away from the heart • Aorta • Right and left pulmonary arteries External Heart: Vessels that Supply/Drain the Heart (Posterior View) • Arteries – right coronary artery (in atrioventricular groove) and the posterior interventricular artery (in interventricular groove) • Veins – great cardiac vein, posterior vein to left ventricle, coronary sinus, and middle cardiac vein Gross Anatomy of Heart: Frontal Section • Frontal section showing interior chambers and valves • Major vessels leading to and from the heart Gross Anatomy of Heart: Frontal Section 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 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 Coronary Circulation • Coronary circulation is the functional blood supply to the heart • Collateral routes insure blood delivery to heart even if major vessels are occluded Heart Valves • Heart valves insure 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 • Aortic semilunar valve lies between the left ventricle and the aorta • Pulmonary semilunar valve lies between the right ventricle and pulmonary trunk • Semilunar valves prevent backflow of blood into the ventricles Microscopic Heart Muscle Anatomy • Cardiac muscle is striated, short, fat, branched, and interconnected • 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 Cardiac Muscle Contraction • Heart muscle: • Is stimulated by nerves and self-excitable (automaticity) • Contracts as a unit • Has a long (250 ms) absolute refractory period • Cardiac muscle contraction is similar to skeletal muscle contraction Heart Physiology: Intrinsic Conduction System • Autorhythmic cells: • Initiate action potentials • Have unstable resting potentials called pacemaker potentials • Use calcium influx (rather than sodium) for rising phase of the action potential Heart Physiology: Intrinsic Conduction System Heart Physiology: Sequence of Excitation • Sinoatrial (SA) node generates impulses about 75 times/minute • Atrioventricular (AV) node delays the impulse approximately 0.1 second • Impulse passes from atria to ventricles via the atrioventricular bundle (bundle of His) Heart Physiology: Sequence of Excitation • AV bundle splits into two pathways in the interventricular septum (bundle branches) • Bundle branches carry the impulse toward the apex of the heart • Purkinje fibers carry the impulse to the heart apex and ventricular walls Extrinsic Innervation of the Heart •
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