About the heart
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 a fist.
At an average rate of 80 times a minute, the heart beats about 115,000 times in one day or about 42 million times in a year. In a 70-year lifetime, an average human heart will beat more than 2.5 billion times. Even when a person is at rest, the heart continuously works hard.
How the heart works
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:
Four chambers (two atria and two ventricles) that receive blue (deoxygenated) blood from the body and pump out red (oxygen-rich) blood back to to it:
Blood vessels, which include a network of arteries and veins that carry blood throughout the body:
Four valves to prevent backward flow of blood:
An electrical system that serves as a natural pacemaker and stimulates contraction of the heart muscle.