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:
“For you are a people holy to the LORD your God; the LORD your God has chosen you out of all the peoples on earth to be his people, his treasured possession. It was not because you were more numerous than any other people that the LORD set his heart on you and chose you -for you were the fewest of all peoples.”
—Bible: Hebrew, Deuteronomy 7:6,7.
“And finally I twist my heart round again, so that the bad is on the outside and the good is on the inside, and keep on trying to find a way of becoming what I would so like to be, and could be, if ... there weren’t any other people living in the world.”
—Anne Frank (1929–1945)
“But as it is written, eye hath not seen, nor ear heard, neither have entered into the heart of man, the things which God hath prepared for them that love him.”
—Bible: New Testament 1 Corinthians 2:9.