How Your Heart Works

When you listen to your heartbeat through a stethoscope ("lubb-dubb, lubb-dubb"), you hear the sound of your heart valves closing.

Your heart valves keep blood flowing in one direction through your heart, just like the one-way valves in your home's plumbing. They open to let blood flow through, and then close to prevent blood from flowing back the way it came. Blood flows through each valve one time on its way through your heart.

The four valves can be grouped by their job:

• The tricuspid valve is between the right atrium and the right ventricle.
• The mitral valve is between the left atrium and the left ventricle.
• Blood flows out of the right ventricle to the lungs through the pulmonary valve.
• Blood flows out of the left ventricle to your body through the aortic valve.

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Your Blood Vessels

Blood flows to and from the heart through tubes called blood vessels. Blood vessels carry blood to every part of your body, "dropping off" oxygen and nutrients and "picking up" waste products and carbon dioxide. Then the blood returns to the heart. There are three types of blood vessels, arteries, capillaries and veins.

Arteries always carry blood flowing away from the heart. Major arteries connected to your heart include:

• The pulmonary artery carries blood pumped from the right side of the heart to the lungs to pick up a fresh supply of oxygen.
• The aorta is the main artery that carries oxygen-rich blood pumped from the left side of the heart out to the body.
• The coronary arteries carry oxygen-rich blood from the aorta to the heart muscle itself. The heart needs its own blood supply to function.

The Coronary Arteries

Capillaries are the tiniest vessels in the body, carrying blood to and from every cell in your body.

Veins are major blood vessels that carry the oxygen-poor blood from the body back to your heart.

• Like coronary arteries, coronary veins work just in your heart. Coronary veins collect the oxygen-poor blood from your heart muscle—from the heart wall, not from inside the heart chambers. The coronary veins empty blood directly into the right atrium. 

Someone you know may have coronary artery disease (CAD). A person with CAD has at least one coronary artery that is clogged and is not letting all the blood through to the heart muscle.

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Your Blood Pressure
Your blood pressure is a measure of the force of your blood pushing against the walls of your arteries. Blood pressure is measured in two numbers—a higher number "over" a lower number.

• The bigger number (on top) is called the systolic pressure. It is a measure of the pressure when your heart is pumping.
• The smaller number (on the bottom) is called the diastolic pressure. It is a measure of the pressure when your heart is resting between beats.

Normal blood pressure for an adult is “120 over 80” or 120/80.

Blood pressure tells your doctor how hard your heart is working. If one or both numbers are higher than normal, you have high blood pressure. High blood pressure means your heart is working extra hard to push blood through your arteries. It also means you may be at higher risk for developing heart problems or disease.

Next: Your Heart at Work >>

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