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:
“Not yet has my heart or head
In the least way realized
They and I are civilized.”
—Countee Cullen (1903–1946)
“Hope deferred makes the heart sick, but a desire fulfilled is a tree of life.”
—Bible: Hebrew, Proverbs 13:12.
“Away, and mock the time with fairest show;
False face must hide what the false heart doth know.”
—William Shakespeare (1564–1616)