The heart weighs
between 7 and 15 ounces (200 to 425 grams) and is a little larger than the size of your
fist. By the end of a long life, a person's heart may have beat (expanded and contracted)
more than 3.5 billion times. In fact, each day, the average heart beats 100,000 times,
pumping about 2,000 gallons (7,571 liters) of blood.
Exterior Heart Picture
Interior Heart Picture
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.