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)
“So immense are the claims on a mother, physical claims on her bodily and brain vigor, and moral claims on her heart and thoughts, that she cannot ... meet them all and find any large margin beyond for other cares and work. She serves the community in the very best and highest way it is possible to do, by giving birth to healthy children, whose physical strength has not been defrauded, and to whose moral and mental nature she can give the whole of her thoughts.”
—Frances Power Cobbe (1822–1904)
“We talk about a representative government; but what a monster of a government is that where the noblest faculties of the mind, and the whole heart, are not represented! A semihuman tiger or ox, stalking over the earth, with its heart taken out and the top of its brain shot away. Heroes have fought well on their stumps when their legs were shot off, but I never heard of any good done by such a government as that.”
—Henry David Thoreau (1817–1862)