Anatomy and Physiology: The Heart
Valentine's Day, at least the greeting card variety, has forever done the anatomist a disservice. We have all grown up seeing the heart as an upside-down butt shape with a point at the opposite end?and don't even get me started on Cupid, with his wings coming out of his back (like an insect), rather than as arms (like a bird or bat)?but the heart looks nothing like that! Luckily, for people with a bit of a sick sense of humor like me, it is now possible to buy life-size, anatomically correct, milk chocolate hearts!
The heart is really a pretty cool organ, with an elegant shape that mirrors its function. Not only amazingly strong, but incredibly sturdy, the heart beats about 100,000 times a day, 36,500,000 times a year (not to mention an extra 25,000 times each leap year, and a total of about 2,739,375,000 times in an average lifetime (approximately 75 years, give or take). Resting for 24 hours will save your heart 20,000 beats, which is why your momma told you to stay in bed and rest when you were sick; just think of all the energy you save! Every day the heart pumps about 8,000 liters of blood, or enough, over the same average lifetime, to fill about 581/2 Olympic-size swimming pools (a total of 219,150,000 liters in a lifetime).
What I love about the heart, despite it not being the seat of the emotions (for that you need to look at the limbic system in the brain; see The Central and Peripheral Nervous Systems), is its subtlety. How the heart coordinates the efficient pumping of four chambers to each of the three circuits simultaneously is the epitome of evolutionary elegance.
Excerpted from The Complete Idiot's Guide to Anatomy and Physiology 2004 by Michael J. Vieira Lazaroff. All rights reserved including the right of reproduction in whole or in part in any form. Used by arrangement with Alpha Books, a member of Penguin Group (USA) Inc.