During the few moments it will take you to read this review, your body will be extremely busy. Your lungs will inhale and exhale about 300 sextillion oxygen molecules. Your bone marrow will create some 200 million red blood cells.Your eyebrows will serve as a buffet for thousands of tiny mites that, as Bill Bryson puts it, munch on our cells as if they are a “giant crusty bowl of Corn Flakes.”I like to remind myself of these mind-boggling (and occasionally disgusting) facts because I so often take my body for granted.One of the strengths of Bryson’s delightful new book, “The Body,” is that it reveals the thousands of rarely acknowledged tasks our body takes care of as we go about our day. We should be thankful.Well, mostly thankful. In some respects, the human body is terribly designed. It’s a collection of evolution’s Scotch-tape-and-bubble-gum fixes (see our injury-prone knees or the dangerously exposed scrotum). Plus, our bodies can and do go horribly awry, whether from tennis elbow or deadly infections.But still, this cluster of interdependent 37.2 trillion cells is all we’ve got — at least until we upload our brains into the cloud. And on the whole, it’s pretty remarkable.Bryson built his career with wry first-person travel books (for instance, “A Walk in the Woods,” about his ill-fated trek on the Appalachian Trail) and has since moved onto popular guides to science and history (“A Short History of Everything,” about, well, everything).This time, Bryson takes us on a body-part-by-body-part tour, with chapters devoted to the brain, the guts and the skin and hair. Each chapter weaves together history, anecdotes, expert interviews and vocabulary lessons. I learned about “horripilation” (the proper name for goose bumps) and “adermatoglyphia” (the rare condition of having no fingerprints).The overall result is informative, entertaining and often gross (kissing, according to one study, transfers up to one billion bacteria from one mouth to another, along with 0.2 micrograms of food bits).Bryson particularly excels at ferreting out unsung heroes. Here, he gives some love to John Charnley, a British orthopedic surgeon, who perfected the artificial hip made of steel and plastic. “Almost no one has heard of Charnley,” Bryson writes, “but few people have brought relief to greater numbers of sufferers than he did.” And Bryson gives much-deserved credit to a woman named Fanny Hesse, albeit in a footnote. Hesse, who was married to a German scientist, suggested growing microbes in agar, which her grandmother used in pudding recipes. Agar turned out to be the perfect habitat for microbes. Hesse likely saved millions of lives by speeding up tuberculosis research and microbiology in general. Thank you, Frau Hesse.Bryson, who gives off a Cronkite-like trustworthy vibe, is good at allaying fears and busting myths. For instance, he says you don’t have to worry about MSG — there’s no science indicating that eating normal amounts of this synthetic umami causes headaches or malaise (though there is evidence people find it delicious). You can also stop obsessing about antioxidants. There’s little science behind the claim that you can increase your life span with antioxidant supplements (a $2- billion-a-year industry).So when a levelheaded guy such as Bryson gets worried, it’s probably wise to worry too. If there’s one part of this book everyone should read, it’s the five pages on the antibiotic crisis. It will light up your amygdala.Because of the continuing overuse of antibiotics on ourselves, our farm animals and even our fruits, we’ve created some really nasty germs. Already the superbug MRSA and its cousins kill an estimated 700,000 people around the world annually, Bryson says. It’s an arms race bacteria are threatening to win, and humans can’t keep up. Pharmaceutical companies aren’t inventing enough new antibiotics because they’re too expensive to develop.If we continue on our current trajectory, we’re talking a dystopian future that looks a lot like the past: infectious diseases overtaking heart disease as the biggest killer. We need new antibiotics so our bodies can continue their amazing, unacknowledged drudge work.A.J. Jacobs’s most recent book is “Thanks a Thousand: A Gratitude Journey.”THE BODYA Guide for OccupantsBy Bill BrysonIllustrated. 446 pp. Doubleday. $30.