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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.
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