1. The gastrointestinal tract is a 30-foot tube running from your mouth to your anus. Topologically, your gut has the same shape as those doughnuts you regularly pass through it.
2. The small intestine contains so many folds — down to the microscopic level — that its total surface area is about 2,700 square feet, enough to cover a tennis court.
3. The Roman physician Galen regarded the stomach as a quasi-autonomous being within us, able to “feel a lack which rouses the animal and stimulates it to seek food.”
