How a Healthy Heart Works

Your circulatory system is made up of your heart, arteries, and veins.

Your heart is a muscular organ, about the size of a man's clenched fist, that lies under the lower part of your breast bone. It's job is to pump oxygen-rich blood out to every cell in your body, where the oxygen is absorbed. The heart is divided into right and left sides, and upper and lower chambers. The upper chambers are the right atrium and left atrium (plural atria). The lower chambers are the right and left ventricles.

The chambers are separated by four valves that open to let the blood through, and close to keep the blood from flowing backwards. They are the mitral valve, which lies between the left atrium and ventricle; the aortic valve, which lies between the left ventricle and the aorta; the pulmonic valve, between the right ventricle and the pulmonary artery; and the tricuspid valve, between the right atrium and ventricle.

Here's how your circulatory system works
Oxygen-poor blood flows from the body to the right atrium, through the valve, and on to the right ventricle. The right ventricle pumps the blood to the lungs, where the blood absorbs oxygen. This oxygenated blood is pumped to the left atrium, down to the left ventricle, into the aorta, and out to the body. After the body has absorbed the oxygen from the arteries, the blood passes on to the veins, where it is carried back to the heart and lungs to get a new supply of oxygen.

The heart itself is nourished by the coronary arteries. The left ventricle, the heart of the pump, contracts and sends the oxygenated blood out through the aorta. The first artery off of the aorta delivers blood through the coronary arteries so they can nourish the heart. There are many coronary arteries that nourish the heart muscle.

Arteries deliver oxygen-rich blood from the heart to the body. The largest artery (in fact, the largest blood vessel in the body) is the aorta, which leads from the heart out to the body. Other arteries branch out from the aorta, forming a network of arteries that get smaller and smaller the further away from the heart they lie. A network of veins takes oxygen-poor blood back to the heart.

What makes your heart beat?
The heart has a kind of electrical system that signals the chambers of the heart to contract and relax in a certain order. When the chambers contract, the blood is forced onward. These contractions make up the lub-dub, lub-dub of your heart beat.

Your heart is triggered to beat by a system of tiny electrical impulses. These impulses start in the sinoatrial node, or SA node, which is a small mass of specialized tissue in the right atrium of the heart. This electrical stimulus travels down along the heart's conduction pathways (the way electricity flows through power lines from the power plant to your house) and makes the heart's chambers contract and pump out blood. Normally, as the electrical impulse moves through the heart, the heart contracts about 60 to 100 times a minute. Each contraction represents one heartbeat. The atria contract a fraction of a second before the ventricles so their blood empties into the ventricles just before the ventricles contract, sending the blood on its way out to the body and its organs.

The lub-dub sounds are made when the heart valves that separate the chambers of the heart open and close in sequence.

One of the most important organs, of course, is the heart itself. Your heart muscle requires a good supply of nutrients and oxygen in order to keep up its steady beat. The heart muscle is fed by arteries that lie on its surface.When those arteries become blocked, the heart muscle is starved, and begins to die. This is what is known as a heart attack.

Anything that interferes with the smooth flow of blood to your heart, lungs, and body, can cause cardiovascular disease. And that is what the staff of The Heart Institute is dedicated to preventing.