About the Heart and Blood Vessels
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The heart is the hardest working muscle in the human body. Located almost in the center of the chest, a normal healthy adult heart is the size of an average clenched adult fist. By age 70, the human heart will beat more than 2.5 billion times. The heart is always working and pumps about 2,000 gallons of blood daily.
A child's heart works just as hard as an adult's heart. In fact, at rest, a baby's heart may beat up to 130 to 150 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 cardiovascular system, composed of the heart and blood vessels, is responsible for circulating blood throughout the body. A healthy cardiovascular system is vital to supplying the body with oxygen and nutrients.
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How the heart works
The heart is a large, muscular organ that pumps blood filled with oxygen and nutrients through the blood vessels to the body tissues. It's made up of:
Four chambers. The two upper chambers, the atria, receive and collect blood. The two lower chambers, ventricles, pump blood to other parts of your body. More specifically:
The right atrium receives blood from the body, which is low in oxygen.
The right ventricle pumps the blood from the right atrium into the lungs to provide it with oxygen and remove carbon dioxide.
The left atrium receives blood from the lungs, which is rich in oxygen.
The left ventricle pumps the blood from the left atrium into the body, supplying all organs with oxygen-rich blood.
Four valves. The four valves: aortic, pulmonary, mitral, and tricuspid valves are designed to allow the forward flow of blood and prevent the backward flow.
Blood vessels. These bring blood to the lungs, where oxygen enters the bloodstream, and then to the body:
The inferior and superior vena cava bring oxygen-poor blood from the body into the right atrium.
The pulmonary artery channels oxygen-poor blood from the right ventricle into the lungs, where oxygen enters the bloodstream.
The pulmonary veins bring oxygen-rich blood to the left atrium.
The aorta channels oxygen-rich blood to the body.
An electrical system that stimulates contraction of the heart muscle.
A network of arteries and veins also carry blood throughout the body:
Arteries transport blood from the heart to the body tissues.
Veins carry blood back to the heart.