Ch18_The%20Heart - The Heart Chapter 18 Introduction The...

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The Heart Chapter 18
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Introduction • The heart - a muscular double pump with 2 functions 1) Its right side receives oxygen-poor blood from the body tissues and then pumps this blood to the lungs to pick up O 2 and dispel CO 2 2) Its left side receives the oxygenated blood returning from the lungs and pumps this blood throughout the body to supply O 2 and nutrients to the body tissues • BVs that carry blood to and from the lungs form the pulmonary (plumonos = lungs) circuit • BVs that transport blood to and from all body tissues form the systemic circuit
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Figure 18.1
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The Heart • Has 2 receiving chambers: right and left atrium (‘entranceway’) - receives blood returning from the 2 circuits • Has 2 main pumping chambers: the right and left ventricles (‘hollow belly’) - pumps blood around the 2 circuits • Hollow cone-shaped organ – typical weight 250-350g - about the size of your fist • The largest organ in the mediastinum - located between the lungs - oblique position with apex lying left to the midline
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Location and Orientation within the Thorax Figure 18.2 Figure 18.2
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Four “Corners” of the Heart • Important for clinicians – imaginary lines that connect the 4 corner points delineate the normal size and location of the heart • Superior right – at costal cartilage of 3 rd rib and sternum • Inferior right – at costal cartilage of 6 th rib lateral to the sternum • Superior left – at costal cartilage of 2 nd rib lateral to the sternum • Inferior left (apex point) – lies in the 5 th intercostal space at the midclavicular line
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Location and Orientation within the Thorax
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Structure of the Heart - Coverings • Pericardium – a triple-layered sac that encloses the heart - fibrous pericarium , strong outer layer of dense CT - serous pericardium , formed from 2 layers: the outer parietal pericardium adheres to the inner surface of the fibrous pericardium and is continuous with the visceral layer or epicardium • Pericardial cavity – between parietal and visceral layers - epithelial cells secrete a lubricating serous fluid - reduce friction between the heart and outer wall of the pericardial sac
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Figure 1.10 Pericardial Serous Cavity
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Layers of the Heart Wall 3 layers - a superficial, middle, deep • Epicardium – visceral layer of the serous pericardium (often infiltrated with fat) • Myocardium – forms the bulk of the heart - consists of cardiac muscle tissue (layer that contracts) - CTs bind the cells into elongated circular and spiral bundles • Endocardium – sheet of endothelium resting on a thin layer of CT - lines the heart chambers and covers the heart valves
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Layers of the Heart Wall Figure 18.3
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Bundles Figure 18.4 • Function to squeeze blood through the heart in the proper directions - inferiorly through the atria - superiorly through the ventricles
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Heart Chambers • Right and Left atria – superior chambers - divided longitudinally by the interatrial septum • Right and Left ventricles – inferior chambers - divided longitudinaly by the interventricular septum
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Ch18_The%20Heart - The Heart Chapter 18 Introduction The...

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