Sometimes too much gets through when people overindulge, which leads to obesity, diabetes, and heart disease. The alimentary canal absorbs and digests nutrients from food, delivering water, proteins, fats, carbohydrates, vitamins, and minerals to the body. The lungs, meanwhile, do an excellent job of keeping themselves clean but can be overwhelmed, especially from smoking and asthma. Human survival depends on the immune system, which protects the body from pathogens that enter through the air, food, or cuts in the skin.

The skeleton provides structure and the leverage to move about, but humans walk vertically on two feet, which puts unusual stresses on the spine and hips and can cause humans to experience pain and disability unique to them in the animal kingdom. The heart and blood distribute oxygen, food energy, and the various biochemicals generated by the body’s organs. The latter take in food and air and send them down a shared tube, the pharynx, that manages eating and breathing so as to enable the miracle of human speech. The next few chapters discuss the head, with its complexly lobed brain major sensors the eyes, ears, and nose and the mouth and throat. One of its principal jobs is to keep out dangerous microbes, yet deep inside, trillions of good microbes colonize the gut, help with digestion, and influence body processes. These atoms are assembled by instructions from the DNA at the center of each of the trillions of cells that make up an adult human.

The Body also contains dozens of anecdotes on the researchers, often unsung, who made the discoveries that led to the great advances of medicine.īryson begins with an inventory of the elements that make up the body: In purified form, they would cost over $150,000. It explores the various organ systems-skin, brain, eyes, nose, mouth and throat, heart and blood, skeleton, lungs, digestive tract-as well as multisystem experiences like digestion and energy production, immunity and disease, sleep, sex, childbirth, old age, and death. Compiled for the general reader, The Body is a compendium of facts, many amazing or weird, about human anatomy and physiology.

The Body by Bill Bryson