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:
“Only ambition is fired by the coincidences of success and easy accomplishment but nothing is quite as splendidly uplifting to the heart as the defeat of a human being who battles against the invincible superiority of fate. This is always the most grandiose of all tragedies, one sometimes created by a dramatist but created thousands of times by life.”
—Stefan Zweig (18811942)
“My heart burnt within me with indignation and grief; we could think of nothing else.... All night long we had only snatches of sleep, waking up perpetually to the sense of a great shock and grief. Every one is feeling the same. I never knew so universal a feeling.”
—Elizabeth Gaskell (1810–1865)
“The impulse to perfection cannot exist where the definition of perfection is the arbitrary decision of authority. That which is born in loneliness and from the heart cannot be defended against the judgment of a committee of sycophants. The volatile essences which make literature cannot survive the clichés of a long series of story conferences.”
—Raymond Chandler (1888–1959)