KidsMD Health Topics

Heart and Blood Vessels

  • The heart is the hardest working muscle in our bodies. A baby’s heart can work harder than an adult’s heart: Up to 190 times a minute versus 60 to 100 times a minute. This rate naturally slows down as your baby grows.

    During an average person’s lifetime, the human heart will beat more than 3 million times, pumping about a million barrels of blood.

    The cardiovascular system—the heart combined with the blood vessels—is responsible for circulating blood throughout the body. It’s vital to supplying the body with oxygen and nutrients.

    Heart Center
    Boston Children's Hospital

    300 Longwood Avenue
    Boston MA 02115

  • Anatomy of the heart

    The heart consists of four chambers that receive blood from the body and pump out blood to it.

    • Atria
      • two upper chambers
      • receive blood coming back to the heart
    • Ventricles
      • two lower chambers
      • pump the blood out to the heart

    The heart also consists of four valves that prevent backward flow of blood. Each valve has flaps, called leaflets, that allow forward flow of blood and prevent the backward flow.

    • 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 - between the left ventricle and aorta

    Valves are flaps that act as one-way inlets for blood entering and leaving the chambers and ventricles.

    How do blood vessels work?

    Blood vessels bring blood to the lungs, where oxygen enters the bloodstream, and then to the body.

    • Inferior and superior vena cavae - bring oxygen-poor (blue) blood from the body into the right atrium
    • Pulmonary artery - moves oxygen-poor (blue) blood from the right ventricle into the lungs, where oxygen enters the bloodstream
    • Pulmonary veins - bring oxygen-rich (red) blood to the left atrium
    • Aorta - sends oxygen-rich (red) blood to the body

    An electrical system controls how fast the heart beats.

    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.
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