Heart is a hollow muscular organ that pumps blood to all parts of the body. The circulatory system is one of the vital systems of the human body and is responsible for distributing oxygen and nutrients to the cells and tissues of the body and carrying away carbon dioxide and other waste products. The circulatory system is made up of the heart, blood and various blood vessels. Circulation is the process by which nutrients, respiratory gases, and metabolic products are transported throughout a living organism, permitting integration among the various tissues. The process includes the intake of metabolic materials, the conveyance of these materials throughout the organism, and the return of harmful by- products to the environment. The heart is the main component of the circulatory system and is considered as its power supply.

The heart must function ceaselessly and continuously because the body's tissues depend on a constant supply of oxygen and nutrients delivered by the flowing blood. If the heart stops pumping blood for more than a few minutes, death will result. The tissues that are affected the most by any fluctuations in the supply of blood are the brain, nerves and the heart muscle itself. If the brain doesn't get a proper supply of blood, death of brain cells results, leading to death of the person. Lowered amounts of blood supply to the heart muscle itself would lower the ability of the heart to pump blood to all parts of the body. This would cause brain damage and death of the person. The human heart is shaped like an upside-down pear and is located slightly to the left of center inside the chest cavity.

The heart consists mostly of muscle, the myocardial cells arranged in ways that set it apart from other types of muscle. The outstanding characteristics of the action of the heart are its contractility, which is the basis for its pumping action, and the rhythmicity of the contraction. This periodic contraction begins in the developing embryo about three weeks after conception and continues throughout the lifetime. Heart muscle differs from its counterpart, skeletal muscle, in that it exhibits rhythmic contractions. The amount of blood pumped by the heart per minute i.e. the cardiac output varies to meet the metabolic needs of the peripheral tissues like muscle, kidney, brain, skin, liver, heart, gastrointestinal tract. The cardiac muscle rests only for a fraction of a second between beats. During the typical life span of a human being, the heart will beat nearly 2.8 billion times and pump169 million liters of blood.

Since prehistoric times people have had a sense of the heart?s vital importance. Cave paintings from 20,000 years ago depict a stylized heart inside the outline of hunted animals such as bison and elephant. The ancient Greeks believed the heart was the seat of intelligence. From the time of Aristotle in the 4th century BC it had been widely believed that the blood vessels contained both blood and air. Galen, the Greco-Roman physician, in the 2nd century AD proved that the arteries contained only blood but still believed that air entered the right side of the heart from the lungs.

Early in the 16th century the idea of a pulmonary circulation?that is, a circular motion of blood through heart and lungs?began to occur to some anatomists. It was the English physician William Harvey who discovered the true nature of the circulation of the blood and of the function of the heart as a pump. Other cultures had their own beliefs regarding the importance of the heart. Many of them believed the heart to be the source of the soul or of the emotions. This idea persists even today in popular culture and various verbal expressions, such as ?heartbreak.? Heart is also considered as a symbol of love and affection.