How Your Heart Works

It is important for you to know as much as possible about how your heart functions in order to have a complete understanding of bypass surgery.

Your heart is a muscle that pumps blood throughout your body. To do its work, your heart needs a constant supply of oxygen-rich blood which it gets from the lungs.

Coronary arteries are blood vessels that wrap around the heart muscle and keep it supplied with oxygen-rich blood. When blood is pumped by the left ventricle, it is forced into the body's largest artery, the aorta, located at the top of the heart. Two coronary arteries, the left main artery and the right coronary artery, branch off the aorta.

The left main artery is about as wide as a drinking straw and less than an inch long. It branches into two narrower arteries: the left anterior descending, which travels down the front side of the heart, and the left circumflex, which circles around the left side and then to the back of the heart. The right coronary artery branches from the aorta, circles around the right side and then to the back of the heart. These arteries are on the outside surface of the heart. They divide into smaller branches, similar to a tree, and go deep into the heart muscle carrying oxygen-rich blood to the cells.

Chambers of the Heart

The heart muscle is divided into four compartments or chambers, with two on the left side and two on the right side.

The upper chamber on each side is called an atrium. The atrium receives and collects blood. The lower chamber on each side is called a ventricle. The ventricles pump blood. The right ventricle pumps blood only to the lungs. The left ventricle is the main pumping chamber of the heart. It pumps blood to all parts of the body except the lungs.

Heart valves

There are four valves that control the flow of blood inside the heart. They are like one-way doors to keep the blood moving in one direction. When the heart beats, the valves close to keep the blood from flowing backward.

How the chambers and valves work together

Oxygen-poor blood that returns from the body collects in the right side of the heart (right atrium). It passes through the tricuspid valve into the right ventricle which pumps it through the pulmonic valve into the lungs where it picks up fresh oxygen.

Oxygen-rich blood coming from the lungs flows into the left side of the heart (left atrium) where it passes through the mitral valve into the left ventricle. It is then pumped through the aortic valve into the aorta (main artery) and all the other arteries. The aorta is the largest artery in the body.

Coronary arteries

Coronary arteries are the blood vessels that wrap around the heart muscle and keep it supplied with oxygen-rich blood. When blood is pumped by the left ventricle, it is forced into the body’s main artery, the aorta, located at the top of the heart.

Two coronary arteries, the left main artery and the right coronary artery, branch off the aorta.