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:
“I know I have the body of a weak and feeble woman, but I have the heart and stomach of a king, and of a king of England, too.”
—Elizabeth I (1533–1603)
“Sweet is the day of sacred rest;
No mortal cares shall seize my breast;
O may my heart in tune be found
Like David’s harp of solemn sound.”
—Isaac Watts (1674–1748)
“Commercial to the core, Elvis was the kind of singer dear to the heart of the music business. For him to sing a song was to sell a song. His G clef was a dollar sign.”
—Albert Goldman (b. 1927)