Heart & Blood Flow

Your Heart

The human heart is a muscle about the size of your fist that lies in the chest, behind and slightly to the left of the breastbone, and between the lungs. It is a remarkable organ that works hard 24 hours per day, pumping blood through a 60,000-mile network of vessels in the body.

The heart is made up of four major chambers: the right atrium, right ventricle, left atrium and left ventricle. The right side of the heart receives blood that is low in oxygen from veins all over the body. It then pumps the blood, through the pulmonary artery, to the lungs where it will become re-oxygenated.The left side of the heart receives this oxygen-rich blood from the lungs. Then, it pumps the blood through the aorta to the rest of the body.

While blood is circulating through the body, it delivers oxygen and nutrients to tissue through the arteries and picks up carbon dioxide through the veins. The veins return the de-oxygenated blood to the right atrium, and the cycle begins again.

Coronary Circulation

As blood circulates through the heart, some of the blood flows into a set of much smaller blood vessels that provide blood directly to the heart. These arteries, called coronary arteries, surround or “crown” the heart. This separate circulatory system, called coronary circulation, keeps the heart nourished and oxygenated. The two main branches of the aorta that nourish the heart are called the right and left main coronary arteries.

Heart Valves

The heart has four valves. Each valve is like a one-way door that keeps the blood in the heart flowing in the same direction. The valves are made up of two or three small but strong flaps of tissue called leaflets. Leaflets open to allow blood to flow through the valve, and close to prevent blood from flowing backward. The opening and closing of the valves is controlled by blood pressure changes within each heart chamber.

The tricuspid valve is positioned in the heart's right side, between the right atrium and right ventricle. The pulmonic valve separates the right ventricle from the pulmonary artery. The mitral valve is positioned in the heart's left side, between the left atrium and the left ventricle. And the aortic valve separates the left ventricle from the aorta.