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:
“People, I just want to say, you know, can we all get along? Can we get along? Can we stop making it, making it horrible for the older people and the kids?
A man cannot know himself better than by attending to the feelings of his heart and to his external actions, from which he may with tolerable certainty judge “what manner of person he is.” I have therefore determined to keep a daily journal.”
—James Boswell (1740–1795)
“The green trees when I saw them first through one of the gates transported and ravished me, their sweetness and unusual beauty made my heart to leap, and almost mad with ecstasy, they were such strange and wonderful things.”
—Thomas Traherne (1636–1674)
“What we call spring here is one rose and two buds that just grew in the cloister garden. That is enough to move the men of my country. But their heart resembles that miserly rose. A more powerful breath would wilt them, they have the spring that they deserve.”
—Albert Camus (1913–1960)