A Normal 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/her fist.
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. The heart rate constantly fluctuates depending on the cardiovascular demands of the body at that moment.
Composed of the heart and blood vessels, the cardiovascular system is responsible for circulating blood (oxygen) throughout the body.
The heart has four chambers:
- Upper right atrium
- Upper left atrium
- Lower right ventricle
- Lower left ventricle
The flow of blood through the heart is controlled by four heart valves. The valves open and close as the blood is pumped through the heart. Each valve has a set of flaps (also called leaflets or cusps). All valves have three flaps, except for the mitral valve. Normally, it only has two. As the heart beats it creates pressure that opens the valves which allows blood to flow through the flaps. They make sure the blood only flows in one direction.
- Tricuspid valve (between the right atrium and right ventricle)
- Pulmonary valve (between the right ventricle and pulmonary artery)
- Mitral valve (between the left atrium and left ventricle)
- Aortic valve (between the left ventricle and the aorta)
The right side receives blood from the body and pumps it to the lungs. The left side receives the blood from the lungs and is pumped out into the body. The heart receives blood from veins and sends blood out through arteries.