The heart is a hollow muscle that pumps blood throughout the blood vessels by repeated, rhythmic contractions. It is found in all animals with a circulatory system (including all vertebrates).
The term cardiac (as in cardiology) means "related to the heart" and comes from the Greek καρδιά, kardia, for "heart".
The vertebrate heart is principally composed of cardiac muscle and connective tissue. Cardiac muscle is an involuntary striated muscle tissue found only in this organ and responsible for the ability of the heart to pump blood.
The average human heart, beating at 72 beats per minute, will beat approximately 2.5 billion times during an average 66 year lifespan. It weighs approximately 250 to 300 grams (9 to 11 oz) in females and 300 to 350 grams (11 to 12 oz) in males.
Read more about Heart: Structure, The Invertebrate Heart, Functioning, Early Development, History of Discoveries, Additional Images
Famous quotes containing the word heart:
“I knew a pure heart who refused tot be mistrustful.... He had written at his doorstep: “From wherever you are, enter and be welcome”. Who do you think responded to this lovely invitation? The militia, who made themselves at home and gutted him.”
—Albert Camus (1913–1960)
“I’ve looked on a lot of women with lust. I’ve committed adultery in my heart many times. This is something God recognizes I will do—and I have done it—and God forgives me for it.”
—Jimmy Carter (James Earl Carter, Jr.)
“The heart has its reasons of which reason knows nothing: we know this in countless ways.”
—Blaise Pascal (1623–1662)