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Anatomy of the Human Heart
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Anatomy of the Human Heart with Flash Illustration
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The heart weighs between 7 and 15 ounces (200 to 425 grams) and is a little larger than the size of your fist.

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Click here for non-Flash version of this illustration and the full text for heart anatomy.

Your heart is located between your lungs in the middle of your chest, behind and slightly to the left of your breastbone (sternum). A double-layered membrane called the pericardium surrounds your heart like a sac. The outer layer of the pericardium surrounds the roots of your heart's major blood vessels and is attached by ligaments to your spinal column, diaphragm, and other parts of your body. The inner layer of the pericardium is attached to the heart muscle. A coating of fluid separates the two layers of membrane, letting the heart move as it beats, yet still be attached to your body.

Your heart has 4 chambers. The upper chambers are called the left and right atria, and the lower chambers are called the left and right ventricles. A wall of muscle called the septum separates the left and right atria and the left and right ventricles. The left ventricle is the largest and strongest chamber in your heart. The left ventricle's chamber walls are only about a half-inch thick, but they have enough force to push blood through the aortic valve and into your body.

Four types of valves regulate blood flow through your heart:

  • The tricuspid valve regulates blood flow between the right atrium and right ventricle.
     
  • The pulmonary valve controls blood flow from the right ventricle into the pulmonary arteries, which carry blood to your lungs to pick up oxygen.
     
  • The mitral valve lets oxygen-rich blood from your lungs pass from the left atrium into the left ventricle.
     
  • The aortic valve opens the way for oxygen-rich blood to pass from the left ventricle into the aorta, your body's largest artery, where it is delivered to the rest of your body.

Updated July 2015
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