Heart

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:

    I cast my heart into my rhymes,
    That you, in the dim coming times,
    May know how my heart went with them
    After the red-rose-bordered hem.
    William Butler Yeats (1865–1939)

    The last time I saw Paris
    Her heart was warm and gay,
    I heard the laughter of her heart in every street café.
    Oscar Hammerstein II (1895–1960)

    I have a heart to love all the world; and like Alexander I wish there were yet other worlds, so I could carry even further my amorous conquests.
    Molière [Jean Baptiste Poquelin] (1622–1673)