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:
“The heart of Paris is like nothing so much as the unending interior of a house. Buildings become furniture, courtyards become carpets and arrases, the streets are like galleries, the boulevards conservatories. It is a house, one or two centuries old, rich, bourgeois, distinguished. The only way of going out, or shutting the door behind you, is to leave the centre.”
—John Berger (b. 1926)
“I knew a pure heart who refused tot be mistrustful.... He had written at his doorstep: “From wherever you are, enter and be welcome”. Who do you think responded to this lovely invitation? The militia, who made themselves at home and gutted him.”
—Albert Camus (1913–1960)
“Mine eye and heart are at a mortal war,
How to divide the conquest of thy sight;
Mine eye my heart thy picture’s sight would bar,
My heart mine eye the freedom of that right.”
—William Shakespeare (1564–1616)