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How the Heart Works

Your heart is a very strong muscle about the size of your fist. Its function is to move blood through your body, bringing oxygen to the tissues and organs.

The Pumping Chambers

The heart is composed of four chambers. The top two chambers are the left atrium and right atrium. The bottom chambers are the left ventricle and right ventricle.

The Route Blood Takes

Blood depleted of oxygen comes from the body and enters the right atrium. It then goes into the right ventricle where it is pumped into the lungs. The lungs remove the carbon dioxide, add oxygen and return the blood to the left atrium. From there the blood goes into the left ventricle where it is pumped out through the aorta (the great artery) and back to the body.

The Valves

The four valves of the heart act as one way doors ensuring the blood flows in the right direction. The picture at right shows where these valves are located.

The Coronary Arteries

While the heart pumps nearly 2,000 gallons of blood each day, it does not get its own oxygen or blood supply directly from the blood that flows through its chambers. The heart's blood supply comes from two main arteries: 

right coronary artery: supplies blood to the right side and bottom of your heart

left main artery (and its branches: the left anterior descending and circumflex arteries): supplies blood to the front left side and back of your heart

When one of these arteries becomes blocked a heart attack occurs!

The Rhythm

The healthy heart beats approximately100,000 times a day. Its rhythm is created and controlled by its own conduction system, which begins with the sinus node located in the right atrium. From here, the impulse travels to the AV node. This node slows it down before it moves through conduction pathways made up of specialized muscle fibers. The fibers distribute the impulse through both ventricles, causing them to contract and pump blood out of the heart. Because the rhythm originates in the sinus node, normal rhythm is called sinus rhythm. Sinus rhythm is regular and pumps at a pace of about 60-100 beats per minute when you are resting, faster when you are exercising.

Atherosclerosis & Plaque

Atherosclerosis involves both the hardening of the artery and the build-up of substances on the inside of the artery. It is a condition that results when cells lining the artery are damaged. Scientists believe this damage comes from uncontrolled high blood pressure, high cholesterol, elevated triglycerides and smoking.

Build-up of fat, cholesterol and other substances on the inside of the artery is called plaque. Most of this comes from the food we eat. As the plaque builds, the artery becomes damaged and narrowed and blood cannot get through as easily.

Coronary Artery Disease

When atherosclerosis is present in the coronary arteries (the arteries that feed the heart), it is called coronary artery disease or CAD. Patients with CAD are at increased risk for angina and heart attack. Typically, when an artery becomes narrowed and blood flow is restricted, CAD will cause symptoms and be recognized as a problem.

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