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:
“There is something about poverty that smells like death. Dead dreams dropping off the heart like leaves in a dry season and rotting around the feet; impulses smothered too long in the fetid air of underground caves. The soul lives in a sickly air. People can be slave-ships in shoes.”
—Zora Neale Hurston (1891–1960)
“They borrow words for thoughts they cannot feel,
That with a seeming heart their tongue may speak;
And in their show of life more dead they live
Than those that to the earth with many tears they give.”
—Jones Very (1831–1880)
“A celibate, like the fly in the heart of an apple, dwells in a perpetual sweetness, but sits alone, and is confined and dies in singularity.”
—Jeremy Taylor (1613–1667)