Your heart is located in the centre of your chest just behind the breastbone (sternum). It is a very strong muscle about the size of a fist.
Your heart works as a pump to deliver blood to your body. Normally, your heart beats about 60-90 times a minute. When you are resting your heartbeat slows; when you exercise or get frightened it speeds up.
Blood carries oxygen and nutrients, which your body needs. Without enough oxygen and nutrients you may experience fatigue, shortness of breath or pain.
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Your heart has a right and a left side. Each side functions as a pump. The right side receives oxygen poor blood from the body and pumps it to the lungs. The left side receives oxygen rich blood from the lungs and pumps it through the body.
The right side has an upper chamber, the right atrium (RA) and a lower chamber, the right ventricle (RV). Blood, which has circulated through the body, enters the right atrium and passes through the tricuspid valve into the right ventricle. The right ventricle then pumps the blood through the pulmonary valve to the lungs where it will receive oxygen.
The left side has an upper chamber, the left atrium (LA) and a lower chamber, the left ventricle (LV). Oxygen rich blood from the lungs enters the heart in the left atrium and passes through the mitral valve into the left ventricle. The left ventricle pumps the oxygen rich blood through the aortic valve to the aorta which delivers it to the rest of the body.
There are four valves in your heart: the mitral, aortic, tricuspid and pulmonary valves. These valves ensure that blood flows in one direction only, by allowing forward flow and preventing backflow of blood through the heart.
Valves may be abnormally formed at birth, or can become damaged later in life due to infections, rheumatic fever, heart attacks, or the normal ageing process that causes calcium build-up. Any of these conditions can result in failure of the valve to open freely (stenosis) or to close completely (regurgitation or insufficiency). The aortic and the mitral valves are the most frequently affected.
Your heart receives the oxygen and nutrients it needs in the blood from blood vessels called coronary arteries. The coronary arteries run along the outer surface of the heart. There are two main arteries: the left and the right, which originate at the base of the aorta as it leaves the heart.
The left main coronary artery divides into two branches. The left anterior descending artery runs down the front (anterior) surface of the heart and supplies blood to a major portion of the left ventricle. The second branch, the circumflex artery, circles around to the left and feeds the side wall of the heart.
The right coronary artery supplies the right ventricle, branches or the electrical system, and the undersurface of the heart.