Heart

Heart

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Heart Location in the Chest

The heart is located slightly left of center in your chest. It is protected from external shock or damage by the thoracic cage, which includes the ribs and sternum.

The heart is part of the cardiovascular system, or more specifically, the circulatory system. It is responsible for pumping blood through the more than 60,000 miles (96,560 km) of arteries, veins and capillaries in your body.

If you visit the doctor, she may listen to your heart using a stethoscope. The doctor may even use a heart monitor to see an electrocardiogram. This is a graph of the electrical activity of the heart. These electrical signals are what makes the heart muscle contract, pumping the blood through your body.

If you put your ear to a friend's chest, you will hear their heart beat. The lub-dup sound is the valves slamming shut, to prevent blood from flowing in the wrong direction.

You can also feel the result of your own heart beat by measuring your pulse. Place two fingers on the inside of your wrist. You should be able to feel the blood pulsing through the blood vessels. Count the number of pulses in 10 seconds, then multiply by 6. This gives your heart rate in beats per minute. The average heart rate is about 70 beats per minute at rest. During exercise, or during stressful situations like watching a scary movie, your heart will beat much faster. Your heart beats faster because your muscles need more oxygen and nutrients to support the increased activity.

The Heart

So, how does the heart work? The heart is primarily a muscle with four hollow chambers and four valves. It is connected to the rest of the circulatory system by major arteries and veins. The heart is about the size of your fist, 5 inches (12 cm) long, 3.5 inches (8-9 cm) wide and 2.5 inches (6 cm) from front to back. It only weights about 10 ounces.

The diagram to the right shows the various components of the heart. The heart can be thought of as having two halves. The right half includes the right atrium and right ventricle, separated by the tricuspid valve. The right half of the heart pumps de-oxygenated blood, and is part of the pulmonary circulation system. It pumps blood to the lungs to pick up oxygen and release carbon dioxide. The left half of the heart includes the left atrium and left ventricle, separated by the mitral valve. It pumps this newly oxygenated blood to rest of the body, and is part of the systemic circulation system.

Blood is pumped out of the heart each time the heart muscle contracts or beats. This is called the systole. This pumping takes place in two stages. First the right and left atria contract pumping blood to the right and left ventricles, respectively. Then the ventricles contract pumping blood out of the heart. The heart muscle then relaxes, called the diastole, so the heart can fill with blood again before the next heartbeat. For more information on blood flow, see the circulatory system and heart blood flow.

Books on the Heart

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Other links on the Heart

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