How a normal heart looks

The normal, healthy heart is a muscle about the size of an adult fist. It weighs about 1 pound. The heart is located near the middle of your chest, slightly to the left. It is a tough muscle designed to work hard and continuously during your life. The heart’s main “job” is to pump blood that carries oxygen and nutrients throughout your body through miles of tubes or blood vessels. Your heart is enclosed in a protective, fiber-like sac called the pericardium.

Heart arteries

There are two arteries on the outside of the heart. They are called coronary arteries and supply blood to the heart.

• The right coronary artery supplies blood to the bottom and back of the heart.
• The left coronary divides into two large blood vessels. They are called the left anterior descending artery and the left circumflex artery. They supply blood to the back, left side and front of the heart.

Heart chambers

Each side of the human heart has two chambers:

• an upper one, called an atrium
• a lower one, called a ventricle

Heart valves

Between each chamber are valves that work like valves on a mechanical pump: they keep fluid (in this case, blood) moving in the right direction:

• tricuspid valve, allowing blood to flow from the right atrium to the right ventricle
• pulmonary valve, allowing blood to flow from the right ventricle to the lungs through the pulmonary artery
• mitral valve, allowing blood to flow from the left atrium to the left ventricle
• aortic valve, allowing blood to flow from the left ventricle to all parts of the body through the aorta

How a normal heart works

The pumping system of a heart is powered by an electrical system that is naturally programmed to tell the heart to beat about 60 to 100 times a minute in an adult. To make a heartbeat:

• An electrical impulse starts in a spot in the upper heart called the sinoatrial (SA) node and travels through the atrium and down to a spot between the atria and ventricals, called the atrioventricular (AV) node.
• The impluse travels through the ventricles.
• When the impulse travels through the atria, it causes them to contract (squeeze) and send blood to the ventricles.
• When the impulse travels through the ventricles, it causes them to contract and send blood to the body.

It is important for the atria and ventricles to contract in a coordinated way to prevent problems.

The right side of your heart receives blood through the veins and pumps it to the lungs to receive new oxygen. The large blood vessel that carries blood from the heart to the lungs is the pulmonary artery.

The left side receives blood with new oxygen from the lungs and sends it out to the body. The large blood vessel that carries blood from the heart to the body is the aorta.

Related Links

What can go wrong with your heart

First published: 10/04/2002
Last updated: 06/01/2007

Reviewed by: Allina Patient Education experts