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Structure and Functioning of Heart

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Heart has two compartments: Left & Right

Both these consists of a pair of chambers formed of muscles. These are upper & lower chambers. Two lower chambers are called left & right ventricle and the two upper chambers are called the left & right atrium.

The walls of heart consist of three main layers. The outer layer, epicardium, is a thin layer that covers the middle layer, myocardium. The myocardium is the heart muscle itself. The inner layer, endocardium, is a thin smooth layer. The entire heart is covered with a protective sac with smooth lining called pericardium.

Structure and Functioning of Heart

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The impure blood carrying carbon dioxide from all parts of body enters the right atrium. It moves into right ventricle through a valve called tricuspid valve. The right ventricle pumps the impure blood into the lungs where the blood gives up the carbon dioxide from all parts of body and absorbs oxygen. This purified blood enters the left atrium first and then the left ventricle through a valve called mitral valve. It finally enters the main artery, aorta, as a result of a very powerful pumping action of the left ventricle. The aorta subdivides into several arteries that supply blood to all parts of the body. Both the left and right sides of the heart contract and relax simultaneously.

The heart pumps blood to itself through special arteries known as coronary arteries. Normally, there are two coronary arteries – right & left. They arise from the main artery, aorta, close to heart and divide into branches that supply blood to heart muscle. Of the two coronary arteries, the left is usually larger and divides into two large branches. The left anterior descending artery and the circumflex artery. The right coronary artery, the left anterior descending artery and the circumflex artery are the three major arteries that supply blood to the heart muscles.

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