A body and its heart
The heart sits in the middle of the chest, behind the breastbone and between the two lungs, with its tip pointing down and to the left. It is about the size of a fist and weighs some 300 grams.
The heart and great vessels from the front, Gray's Anatomy, 20th edition, 1918, figure 490Wikimedia Commons, Henry Vandyke Carter, Public domain (Gray490.png)
At rest it beats about 70 times a minute, some 100,000 times a day, and each beat sends about 70 millilitres of blood on its way.
The body holds about five litres of blood. At rest the heart pumps roughly that volume every minute, so the whole of the blood goes round about once a minute. In hard exercise the output rises four times or more.
Sources
- Susan Standring (ed.), Gray's Anatomy, 42nd ed. (2020), chapter on the heart.
- Arthur Guyton and John Hall, Textbook of Medical Physiology, 13th ed. (2016), ch. 9 and 14.
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