ANATOMY AND PHYSIOLOGY OF THE HEART
The heart and heart wall layers:
The heart is located in the left side of the mediastinum; it consists of three muscle layers the Endocardium, myocardium, and epicardium. The epicardium is the outermost layer of the heart. The myocardium is the idle layer of and actual contracting muscle of the heart. The endocardium is the innermost layer and lines the inner chambers and heart valves. Pericardial sac:
The pericardial sac encases and protects the heart from trauma and infection. The pericardial sac has two layers which are the parietal pericardium which is the tough, fibrous outer membrane that attaches anteriorly to the lower half of the sternum, posteriorly to the thoracic vertebrae, and inferiorly to the diaphragm. The visceral pericardium is the thin inner layer that closely adheres to the heart. The pericardial space is between the parietal and visceral layers it holds 5 to 20 ml of pericardial fluid lubricates the pericardial surfaces and cushions the heart. Chambers:
There are four heart chambers two upper atria (right and left) and two lower ventricles (right and left). The right atrium receives deoxygenated blood from the body via the superior and inferior vena cava. The right ventricle receives blood from the right atrium and pumps it to the lungs via the pulmonary artery. The left atrium receives oxygenated blood from the lungs via four pulmonary veins. The left ventricle is the largest and most muscular chamber. It receives oxygenated blood from the lungs via the left atrium and pumps blood into the systemic circulation via the aorta. Valves:
There are four valves in the heart two atrioventricular (AV) valves – the tricuspid and the mitral – that lie between the atria and ventricles. The tricuspid is located on the right side of the heart. The bicuspid or mitral valve is located on the left side of the heart. The AV valves close at the beginning of the ventricular contraction...
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