A Child's Heart
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 fist. During an average lifetime, the human heart will beat more than three billion times - pumping an amount of blood that equals about one million barrels. The heart is always working, 24 hours a day, seven days a week - even while we are sleeping.
A child's heart works just as hard as an adult's heart. In fact, a baby's heart may beat up to 190 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.