1 Ch 20 The Heart Part 1 1 The Pulmonary Circuit A Heart Circuits Blood alternates between pulmonary circuit and systemic circuit a Carries blood to and from gas exchange surfaces of lungs b Performed by the right side of the heart Right ventricle pushes blood to pulmonary trunk through the pulmonary semilunar valve c Pulmonary trunk divides into left and right pulmonary arteries leads to the left and right lungs respectively 2 The Systemic Circuit a Carries blood to and from the body b Performed by the left side of the heart B Three Types of Blood Vessels 1 Arteries Carry blood away from heart 2 Veins Carry blood to heart 3 Capillaries Also called exchange vessels a Networks between arteries and veins b Location where dissolved gases nutrients and waste products are exchanged between blood and tissue C Four Chambers of the Heart 1 Right atrium Collects blood from systemic circuit a Superior vena cava Receives blood from head neck upper limbs and chest b c Coronary sinus Cardiac veins return blood to coronary sinus Inferior vena cava Receives blood from trunk viscera and lower limbs I Coronary sinus opens into right atrium to be delivered to pulmonary circuit d Foramen ovale Connects the two atria I Before birth is an opening through interatrial septum bypasses right ventricle why important Does not serve purpose to pump blood to your lungs because not exposed to oxygen in sac II Seals off at birth within 3 months of delivery forming a shallow depression called the fossa ovalis 2 Right ventricle Pumps blood to pulmonary circuit a Free edges attach to chordae tendineae from papillary muscles of ventricle I Prevent valve from opening backward muscles tense before ventricular contraction b Right atrioventricular AV valve also called tricuspid valve has three cusps I Opening from right atrium to right ventricle II Prevents backflow of blood 3 Left atrium Collects blood from pulmonary circuit a Blood gathers into left and right pulmonary veins b Pulmonary veins deliver to left atrium c Blood from left atrium passes to left ventricle through left atrioventricular AV valve I A two cusped bicuspid valve or mitral valve 4 Left ventricle Pumps blood to systemic circuit a Holds same volume as right ventricle b c Systemic circulation Is larger muscle is thicker and more powerful why I Blood leaves left ventricle through aortic valve into ascending aorta II Ascending aorta turns aortic arch and becomes descending aorta D Structural Differences between the Left and Right Ventricles 1 Right ventricle wall is thinner develops less pressure than left ventricle 2 Right ventricle is pouch shaped left ventricle is round 3 Damage death of cells in right ventricle survivable since contraction of left ventricle also squeezes right ventricle and push blood into the lungs 2 The Heart Involuntary muscular pump located in thoracic cavity A Typical adult heart is about 5 inches from the base superior to apex pointed tip inferior B Great veins and arteries at the base C Surrounded by pericardial sac D Sits between two pleural cavities in the mediastinum E The Pericardium Double lining of the pericardial cavity 1 Visceral pericardium Inner layer of pericardium 2 Parietal pericardium Outer layer a Forms inner layer of pericardial sac fibrous tissue that surrounds and stabilizes the heart 3 Pericardial cavity between parietal and visceral layers contains pericardial fluid secreted by the pericardial membranes lubricates and prevents friction Infection of pericardium causing inflammation pericarditis F Superficial Anatomy of the Heart 1 Atria Thin walled upper chambers of the heart 2 Sulci grooves that separates the chambers a Coronary sulcus divides atria and ventricles b Anterior and posterior Interventricular sulcus Separate left and right ventricles I Contain blood vessels of cardiac muscle 3 The Heart Wall consists of a Epicardium outer layer consists of I Visceral pericardium that covers the heart b Myocardium middle layer muscular wall of the heart consists of I Concentric layers of cardiac muscle tissue Atrial myocardium wraps around great vessels II Two divisions of ventricular myocardium wraps around both ventricles c Endocardium inner layer of epithelium endothelium lines surface of chambers G Internal Anatomy and Organization 1 2 3 Atrioventricular AV valves folds of fibrous tissue that extend into openings between atria Interatrial septum separates atria Interventricular septum separates ventricles and ventricles a Connect right atrium to right ventricle and left atrium to left ventricle b Permit blood flow in one direction from atria to ventricles c Rheumatic fever inflammatory autoimmune response to streptococcal infection Most often in children Can cause carditis inflammation of the heart and damage heart valves d Two pairs of one way valves prevent backflow during contraction e Blood pressure closes valve cusps during ventricular contraction f Papillary muscles tense chordae tendineae to prevent valves from swinging into atria If chordae tendineae or papillary muscles damaged backflow regurgitation of blood g into atria would occur 4 Semilunar valves a Pulmonary and aortic tricuspid valves b Prevent backflow from pulmonary trunk and aorta into ventricles c Have no muscular support no papillary muscles d Three cusps support like tripod 5 Aortic Sinuses At base of ascending aorta a Sacs that prevent valve cusps from sticking to aorta b Origin of right and left coronary arteries vessels that bring blood to cardiac tissue c Blood drained from cardiac tissue by cardiac veins merge together at coronary sinus H Cardiac Muscle Tissue 1 cardiac muscle cells connected by a Intercalated discs I Secured by desmosomes tightly link cells together II Convey force of contraction b Gap junctions link cytoplasm of cells together I Propagate action potentials 2 Characteristics of Cardiac Muscle Cells a Small size b Single central nucleus c Branching interconnections between cells d Intercalated discs 3 The cardiac skeleton A Connective Tissues and the Cardiac Skeleton 1 Connective tissue fibers composed of elastic and collagen fibers Each cell is wrapped by elastic sheath adjacent cells wrapped by collagen fibers a Physically support cardiac muscle fibers b Distribute forces of contraction c Add strength and prevent overexpansion of heart d Provide elasticity that helps return heart to original size and shape after contraction 2 The Cardiac or fibrous skeleton a Four bands around heart valves and bases of
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