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From the moment it begins beating until the moment it stops, the human heart works tirelessly. In an average lifetime, the heart beats more than two and a half billion times, without ever pausing to rest. Like a pumping machine, the heart provides the power needed for life.

This life-sustaining power has, throughout time, caused an air of mystery to surround the heart. Modern technology has removed much of the mystery, but there is still an air of fascination and curiosity.

The heart you see drawn on the average Valentine is only a rough representation of the actual structure of the heart. Your heart is actually shaped more like an upside-down pear.

The human heart is primarily a shell. There are four cavities, or open spaces, inside the heart that fill with blood. Two of these cavities are called atria. The other two are called ventricles. The two atria form the curved top of the heart. The ventricles meet at the bottom of the heart to form a pointed base which points toward the left side of your chest. The left ventricle contracts most forcefully, so you can best feel your heart pumping on the left side of your chest.

The left side of the heart houses one atrium and one ventricle. The right side of the heart houses the others. A wall, called the septum, separates the right and left sides of the heart. A valve connects each atrium to the ventricle below it. The mitral valve connects the left atrium with the left ventricle. The tricuspid valve connects the right atrium with the right ventricle.

The top of the heart connects to a few large blood vessels. The largest of these is the aorta, or main artery, which carries nutrient-rich blood away from the heart. Another important vessel is the pulmonary artery which connects the heart with the lungs as part of the pulmonary circulation system. The two largest veins that carry blood into the heart are the superior vena cava and the inferior vena cava. They are called "vena cava" because they are the "heart's veins." The superior is located near the top of the heart. The inferior is located beneath the superior.
A human being's heart is about the size of that human being's fist. As the body develops, the heart grows at the same rate as the fist. So an infant's heart and fist are about the same size at birth. In the womb, however, that similarity was not always true. During the first few weeks after conception, the fetal heart occupies most of the fetus' mid-section. The heartsize to bodysize ratio is nine times greater in the fetus than in the infant. During those first few weeks, the fetal heart lies high in the chest. Soon, it moves down to occupy its position in the chest cavity.
There are several phases of the fetal heart's development. At first, the heart is just a tube. It grows so fast that it needs more space, so it bends and twists back, forming the familiar shape. During the next phase, the two atria are partly separate but there is just one big ventricle. The next phase begins when the two atria are completely separate and the ventricles are just beginning to separate. Finally, the ventricles separate completely and the heart is developed.

During the fetal heart's developmental stages, the heart actually takes on several distinct appearances. These heart structures resemble other animal hearts. During phase one, the tube-like heart is much like a fish heart. The second phase, with two chambers, resembles a frog heart. The three-chambered phase is similar to a snake or turtle heart. The final four-chambered heart structure distinguishes the human heart.

The heart's structure makes it an efficient, never-ceasing pump. From the moment of development through the moment of death, the heart pumps. The heart, therefore, has to be strong. The average heart's muscle, called cardiac muscle, contracts and relaxes about 70 to 80 times per minute without you ever having to think about it. As the cardiac muscle contracts it pushes blood through the chambers and into the vessels. Nerves connected to the heart regulate the speed with which the muscle contracts. When you run, your heart pumps more quickly. When you sleep, your heart pumps more slowly.

Considering how much work it has to do, the heart is surprisingly small. The average adult heart is about the size of a clenched fist and weighs about 11 ounces (310 grams). Located in the middle of the chest behind the breastbone, between the lungs, the heart rests in a moistened chamber called the pericardial cavity which is surrounded by the ribcage. The diaphragm, a tough layer of muscle, lies below. As a result, the heart is well protected.

To monitor the heart, scientists can use x-ray or scanning technology to get a picture. To really explore the heart, scientists have to perform surgery. Heart surgery is very risky because the heart's pumping action is so critical for survival. If the heart stops pumping, the body cannot survive. Before beginning heart surgery, doctors connect the patient to a machine that pumps the blood for the heart. Only then is it safe for the doctor to stop the heart in order to operate.If you want your heart to be healthy for the rest of your life, follow this prescription:

1. Get plenty of exercise.

2. Follow a good diet.

3. Keep your heart clean and drug-free.

People who don't follow this prescription often develop some form of heart disease.

Be heart smart and have a healthy heart.

Heart Healthy Living At Any Age

At all stages of life, with the exception of infancy and toddler years, important measures can be taken to protect one's heart from early and unnecessary disease. Core recommendations cross all groups after 2 years of age. Included are dietary practices, physical activity, weight management and avoidance of smoking.

Specific concerns or strategies to best implement the recommendations differ with the age group, however, because stage of life influences many choices, needs and motivations.

Protecting Your Heart

Leading a healthy lifestyle certainly reduces your risk of developing heart disease. Take the following quiz to find out if you are doing all you can to protect yourself.

Answer True or False

1. I don't smoke. True False
2. I exercise regularly. True False
3. I eat a balanced diet. True False
4. I maintain a healthy weight. True False
5. I limit my alcohol intake. True False
6. I effectively manage my stress. True False
7. I limit my intake of saturated fats True False
8. I limit my dietary fat intake. True False
9. I limit my dietary cholesterol. True False
10. I limit my dietary sodium intake. True False
11. I eat soluble fiber True False
12. I have regular physical exams and follow my physician's advice to lower my heart disease risks True False

If you answered True to all of the questions, you are leading a heart healthy lifestyle.

If you answered False to one or more of the questions, you might be at risk for having an
unhealthy heart.

It's never too late to start....