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:
“Night City was like a deranged experiment in Social Darwinism, designed by a bored researcher who kept one thumb permanently on the fast-forward button. Stop hustling and you sank without a trace, but move a little too swiftly and you’d break the fragile surface tension of the black market; either way, you were gone ... though heart or lungs or kidneys might survive in the service of some stranger with New Yen for the clinic tanks.”
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“He prayed more deeply for simple selflessness than he had ever prayed before—and, feeling an uprush of grace in the very intention, shed the night in his heart and called it light. And walking out of the little church he felt confirmed in not only the worth of his whispered prayer but in the realization, as well, that Christ had become man and not some bell-shaped Corinthian column with volutes for veins and a mandala of stone foliage for a heart.”
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“Christ is my onely head,
My alone onely heart and breast,
My onely musick, striking me ev’n dead;”
—George Herbert (1593–1633)