The heart is the hardest working muscle in the human body. Located almost in the center of the chest, the adult human heart is about the size of one fist.
At an average rate of 80 times a minute, the heart beats about 115,000 times in one day or 42 million times in a year. During an average lifetime, the human heart will beat more than 3 billion times, pumping an amount of blood that equals about 1 million barrels. Even when a person is at rest, the heart is continuously hard at work.
The cardiovascular system, composed of the heart and blood vessels, is responsible for circulating blood throughout your body to supply the tissues with oxygen and nutrients.
The heart is the muscle that pumps blood filled with oxygen and nutrients through the blood vessels to the body tissues. It is made up of: