Ch 20-Heart.docx - Basics of The Heart Shape o In the...

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Basics of The Heart Shape o In the thoracic cavity near anterior chest wall, posterior to sternum o Base: sits posterior to the sternum at the level of the 3 rd costal cartilage (right lateral posteriorly) & contains great veins and arteries attached o Apex: pointed tip of the heart; near the left 5 th intercostal space (intro left lateral anteriorly) o Location: Sits in the anterior portion of the mediastinum (region b/w 2 plural cavities) o Size varies by age, height, weight & sex, but roughly the size of clenched fist o B/w 2 nd and 5 th intercostal space PMI: farthest outwards and downwards cardiac impulse can be felt The Heart Wall o Pericardium/Epicardium: towards outside (same as visceral pericardium) o Myocardium: thickest portion & spiral bundle of cardiac muscle cells that contains blood vessels, nerves, and connective tissue o Endocardium: has simple squamous endothelium and continuous w/ endothelial lining of blood vessels Pericardium o Outer Fibrous pericardium: dense network of collagen fibers that stabilize position & vessels of heart within mediastinum o Inner serous pericardium: contains parietal layer and inner visceral layer (epicardium). Pericardial cavity: fluid-filled space b/w two serous layers Pericardial fluid (15-50 mL); acts as lubricant, reducing friction o Visceral epicardium: covers surface of the heart and exposed mesothelium & underlying layer of areolar connective tissue Functions of Pericardium o 1) Anchors the heart to the surrounding tissue o 2) Compartmentalizes the mediastinum separating it from surrounding structures o 3) Physically protects the heart o 4) Prevents Pericarditis: inflammation due to pathogens in pericardium o 5) The pericardial fluid facilitates the movement of the heart Excessive pericardial fluid = pericardial effusion Fluid in pericardial cavity restricting movement of heart = pericardial tamponade Superficial Anatomy of the Heart o Auricle: expandable extension of an atrium o Coronary sulcus: Deep groove, marks the border b/w the atria and ventricles o Depressions of the heart: Coronary sulcus: base of heart separating superior thinner chamber of heart from inferior muscular chamber of heart
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Anterior & posterior interventricular sulcus: shallower depressions that mark the boundary b/w left & right ventricles Both interventricular sulci & coronary sulcus contain fat, arteries & veins Internal Anatomy of the Heart o Interatrial septum: separates atria o Interventricular septum: separates ventricles; much thicker Four Chambers of the Heart o Oxygen poor blood (pulmonary): from right ventricle left atrium o Oxygen rich blood (systemic): from left ventricle right atrium o Systemic circuit: transports blood to and from rest of body o Pulmonary circuit: carries blood to and from the gas exchange surfaces of lungs o Atria: thin walled, receiving chambers o Ventricle: thick walled The Heart Valves o Two pairs of one-way valves prevent backflow during contraction o Atrioventricular (AV) valves: (Tricuspid & Mitral)
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