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:
“My own heart let me more have pity on; let
Me live to my sad self hereafter kind,
Charitable; not live this tormented mind
With this tormented mind tormenting
yet.”
—Gerard Manley Hopkins (1844–1889)
“Give me that man
That is not passion’s slave, and I will wear him
In my heart’s core, ay, in my heart of heart,
As I do thee.”
—William Shakespeare (1564–1616)
“You would rouse to anger a heart of stone.”
—Sophocles (497–406/5 B.C.)