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:
“Who ere shee bee,
That not impossible shee
That shall command my heart and mee;”
—Richard Crashaw (1613?–1649)
“Fine art is that in which the hand, the head, and the heart of man go together.”
—John Ruskin (1819–1900)
“Whoever wants to know the heart and mind of America had better learn baseball, the rules and realities of the game.”
—Jacques Barzun (b. 1907)