Nothing makes a child giggle harder and more dependently than toilet humor. Somewhere on his path to adulthood, however, after constant parental scoldings, an external maturity develops. But that affinity for fart and poop jokes remains, albeit suppressed.

Rather than avoid these taboos, Mary Roach embraces them and teaches us something in the process. Her latest book, “Gulp: Adventures on the Alimentary Canal,” takes us on a journey inside the human body starting from the upper orifices and ending in the lower ones. Along the way, we learn about the science investigating the inner workings of our digestive tracts, and giggle with glee as Roach asks her subjects the questions we’re all wondering but are too polite to ask.

By now, Roach, who wrote the wonderful “Bonk,” which explores sex research, and “Stiff,” which is the definitive book on dead bodies, has settled into a solid formula: pick an unusual topic and report on the experts and relevant literature, all while focusing on the most interesting elements. Readers of her previous works will already know exactly what to expect, but that is by no means a sign of laziness — indeed, no matter what subject she tackles, Roach remains compelling and very, very funny.

Throughout the book, readers will learn about professional taste testers, how the tongue was once used as a scientific instrument, exactly how much humans can smuggle using their internal cavities, the various advantages and disadvantages to using one entrance over the other, if an animal can be eaten from the inside out, whether constipation or internal gas can kill you and pretty much anything else you’ve wanted to know about the workings of your digestive system.

Roach bombards the reader with information, using little more than her enthusiasm and sly sense of humor to propel the book from one topic to another, filling page after page with factoids galore along with footnotes on nearly every page, ensuring that those who pick up the book will have plenty of material to use to pepper their party conversations for months to come.

And, while Roach doesn’t shy away from cheap jokes (how could she resist, given the material?), she also takes moments to be oddly affecting. The final chapter, which deals with fecal transplants (a procedure that, for people with certain disorders, improves the quality of their intestinal flora), would, in another writer’s hands, turn into an easy opportunity to garner laughs. Instead, Roach presents the material with respect and appreciation of the people whose lives are vastly improved by this miracle procedure … which consists of swallowing somebody else’s poop.

“Gulp” is by no means perfect. Even at 352 pages, the book is too short, given the subject matter — then again, it probably could have easily have gone on another 100 pages and still ended too quickly. Additionally, it jumps from one topic to another with little more to transition than a slightly awkward sentence or two at the end of each chapter — right when we’re really getting into a subject, Roach jumps to another one.

However, both of these criticisms stem from just how much fun the book is. If you’ve ever needed to hold in a laugh because of gas that you couldn’t, “Gulp” belongs at the top of your to-read pile.