
The heart is the hardest working muscle in the human body. Located almost in the center of the chest, the heart of a child is about the size of his/her fist. By the age of 70 years old, the human heart will beat more than 2.5 billion times. The heart is always working, 24 hours a day, seven days a week - even while we are sleeping, and pumps about 2,000 gallons of blood daily.
A child's heart works just as hard as an adult's heart. In fact, at rest, a baby's heart may beat up to 140 times a minute, while an adult's heart usually beats between 60 and 100 times a minute. The rate at which the heart pumps gradually slows down from birth to adolescence.
Composed of the heart and blood vessels, the cardiovascular system is responsible for circulating blood throughout the body. A healthy cardiovascular system is vital to supplying the body with oxygen and nutrients.

The heart is a large, hollow, muscular organ that pumps blood filled with oxygen and nutrients through the blood vessels to the body tissues. It is made up of:
A network of arteries and veins also carry blood throughout the body.
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