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:
“Anguish devours the mind, and furious rage, and hope
than which the heart can bear no heavier burden, when
it is long deferred.”
—Publius Papinius Statius (c. 40–96)
“The pleasure of leaving home, care-free, with no concern but to enjoy, has also as a pendant the pleasure of coming back to the old hearthstone, the home to which, however traveled, the heart still fondly turns, ignoring the burden of its anxieties and cares.”
—Herman Melville (1819–1891)
“The heart is blind; but love is not blind. None of the gods is so discriminating.”
—Henry David Thoreau (1817–1862)