Tuesday, November 13, 2012

Cardiac Anatomy: Basic


Average human heart weights about 325 g in men and 275 g in women and 12 cm in length about the size of human fist. It is located in the mediastinum, between the lower lobes of each lung, and rests upon the diaphragm. It is enclosed in a sac called peritoneum. The cardiac wall is composed of 3 layers outer epicardium, middle and inner endocardium. Heart has four chambers 2 atrium and 2 ventricles connected by atrioventricular valve. Pulmonary artery (and to the lungs) receives blood from right AV valve and pulmonary vein empties and aorta (and to the system) flooded through left AV valve. 

(Source: Bishop clinical chemistry, 4th edition)

Right and left coronary artery originating from aortic valve provide blood flow and nutrition to the heart. Epicardium is highly vascularized with large vessels but the endocardium is must susceptible to ischemia because its perfusion relies on small vessels, there wall stress is greatest and opposition to flow occurs.

The myocardium contains muscle fibers composed of cardiac specific contractile proteins actin and myosin, and regulatory troponins. They also contain variety of enzymes like myoglobin, creatine kinase, lactate dehydrogenase, etc.
The systolic to diastolic pressure of heart of BP is 120/80. I.e. during systole the normal blood pressure in the aorta is 120 mm Hg (blood pumped from left ventricles to system). During diastole this pressure in aorta falls to 80 mmHg, during this process atria are being filled with blood. 
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