The adult human heart is about the size of two clenched fists.

In an average lifetime, the heart pumps 1 million barrels of blood- enough blood to fill 3.3 supertankers. This only takes into account  its work at rest. During exercise or stress, the heart may pump ten times as much blood as it does at rest.

In one year, the human heart beats 3 million times. The heart of a 70-year-old has beaten more than 2.5 billion times.

Even when a person is at rest, the muscles of the heart work twice as hard  as the leg muscles of a person running at top speed.

The amount of energy expended by the heart in 50 years is enough to lift a battle ship out of the water.

The electrical signal produced by the sinus node travels over the entire surface of the heart in only 21/100 to 26/100 of a second.

Stretched end to end, the vessels of the circulatory system-arteries, arterioles, capillaries, venules, and veins-would measure about 60,000 miles.

The oxygen and nutrients transported in the bloodstream and delivered with each beat of the heart nourish 300 trillion cells.

The capillaries, the smallest blood vessels in the body, are so tiny that ten of them together are only as thick as a human hair.

In total area the capillary walls are equal to about 60,000 to 70,000 square feet, or roughly the area of one and a half football fields.