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 heart doth joy that yet in all my life
I found no man but he was true to me.”
—William Shakespeare (1564–1616)
“If any ambitious man have a fancy to revolutionize, at one effort, the universal world of human thought, human opinion, and human sentiment, the opportunity is his own—the road to immortal renown lies straight, open, and unencumbered before him. All that he has to do is to write and publish a very little book. Its title should be simple—a few plain words—”My Heart Laid Bare.” But—this little book must be true to its title.”
—Edgar Allan Poe (1809–1845)
“I fairly confess that, acting as nature and simplicity dictated, no sooner did I see the once loved bosom of my Ferdinand free from those deformed demons which had crept in and filled up the vacant space, than beholding my natural home once more the seat of innocence and truth, my heart joyfully danced into its delightful abode.”
—Sarah Fielding (1710–1768)