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:
“He hath a heart as sound as a bell and his tongue is the clapper, for what his heart thinks, his tongue speaks.”
—William Shakespeare (1564–1616)
“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.
“Lady Dellwyn ... for the first time began to entertain some suspicions that she had a heart to bestow. Not that she was actuated by that romantic passion which creates indifference to every other object and makes all happiness to consist in pleasing the beloved person, [but] only overstraining delicacy so much as to feel it almost a crime to charm any other.”
—Sarah Fielding (1710–1768)