.]]The 'heart is a muscular organ responsible for pumping blood through the blood vessels by repeated, rhythmic contractions, or a similar structure in the annelids, mollusks, and arthropods.. The term cardiac (as in cardiology) means "related to the heart" and comes from the Greek ??????, kardia, for "heart." The heart is composed of cardiac muscle, an involuntary muscle tissue which is found only within this organ. The average human heart beating at 72 BPM, will beat approximately 2.5 billion times during a lifetime of 66 years. Early development , the human heart begins beating at 70 to 80 beats per minute and accelerates linearly for the first month of beating.]]It is unknown how blood in the embryo circulates for the first 21 days in the absence of a functioning heart, although some have hypothesized that the heart is not so much a pump, as a Hydraulic Ram -- an organ built-up from cumulative

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