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:
“A woman’s heart must be of such a size and no larger, else it must be pressed small, like Chinese feet; her happiness is to be made as cakes are, by a fixed receipt.”
—George Eliot [Mary Ann (or Marian)
“My heart is set.
All goodly sport
For my comfort
Who shall me let?”
—Henry VIII, King Of England (1491-1547)
“What we call spring here is one rose and two buds that just grew in the cloister garden. That is enough to move the men of my country. But their heart resembles that miserly rose. A more powerful breath would wilt them, they have the spring that they deserve.”
—Albert Camus (1913–1960)