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The heart of a vertebrate is composed of cardiac muscle, an involuntary muscle tissue which is found only within this organ. The average human heart beating at 72 BPM, will beat approximately 2.5 billion times during a lifetime spanning 66 years.

Source: http://www.wikipedia.com

The role of the heart is to pump oxygen-rich blood to every living cell in the body. In order to achieve its goal, it must continuously beat for a person’s entire lifespan. Because of its vital role, a non-beating heart always results in death. The human heart beats approximately 80,000 to 100,000 a day and pumps almost 2,000 gallons of blood. This means that in a person’s life lasting 70 to 90 years, the heart beats approximately two to three billion times and pumps 50 to 65 million gallons of blood. Because the heart is so essential for human sustenance, it is made up of a muscle different from skeletal muscle that allows it to constantly beat. In order for the heart to deliver oxygenated blood to all cells, blood is pumped through arteries. Veins bring deoxygenated blood cells to the lungs, which then are oxygenated, and then sent back to heart. In this way, a continuous cycle is formed of the heart pumping oxygenated blood and deoxygenated blood out to their designated destinations, and therefore the heart maintains the circulatory system.

source: http://library.thinkquest.org