Excerpt from The Body by Bill Bryson, plus links to reviews, author biography & more

Today the problem is as likely to be overtreatment as under, according to some authorities. Balloon angioplasties as a treatment for angina (or chest pains) are a case in point, it seems. With an angioplasty, a balloon is inflated inside a constricted coronary blood vessel to widen it, and a stent, or piece of tubular scaffolding, is left behind to keep the vessel permanently open.* The operation is unquestionably a lifesaver in emergencies, but it has also proven highly popular as an elective procedure. By 2000, a million precautionary angioplasties were being undertaken in the United States every year, but without any proof that they saved lives. When clinical trials were finally undertaken, the results were sobering. According to The New England Journal of Medicine, for every one thousand non-emergency angioplasties in America, two patients died on the operating table, twenty-eight suffered heart attacks brought on by the procedure, between sixty and ninety experienced a "transient" improvement in their health, and the rest—about eight hundred people—experienced neither benefit nor harm (unless of course you count the cost, the loss of time, and the anxiety of surgery as harm, in which case there was plenty).

Despite this, angioplasties remain extremely popular. In 2013, the former president George W. Bush had an angioplasty at the age of sixty-seven, even though he was in good shape and had no sign of heart problems. Surgeons don't usually publicly criticize colleagues, but Dr. Steve Nissen, head of cardiology at the Cleveland Clinic, was scathing. "This is really American medicine at its worst," he said. "It's one of the reasons we spend so much on medicine and don't get a lot for it."



II


HOW MUCH BLOOD you have depends, as you might suppose, on how big you are. A newborn baby contains only about eight ounces, whereas a fully grown man will have more like five quarts. What is certain is that you are suffused with the stuff. Prick your skin any-where and you will draw blood. Within your modest frame are some twenty-five thousand miles of blood vessels (mostly in the form of tiny capillaries), so no part of you is ever far from the refreshment of hemoglobin, the molecule that transports oxygen throughout your body.

We all know that blood carries oxygen to our cells—it is one of the few facts about the human body that everyone does seem to know—but it also does a whole lot more. It transports hormones and other vital chemicals, carries off wastes, tracks down and kills pathogens, makes sure oxygen is directed to the parts of the body where it is most needed, signals our emotions (as when we blush from embarrassment or grow red with fury), helps to regulate body temperature, and even enables the complicated hydraulics of the male erection. It is, in short, a complex material. By one estimate, a single drop of blood may contain four thousand different types of molecules. That's why doctors are so fond of blood tests: your blood is positively packed with information.

Spin a test tube of blood in a centrifuge and it will separate into four layers: red cells, white cells, platelets, and plasma. Plasma is the most abundant, constituting a little over half of blood's volume. It is more than 90 percent water with some salts, fats, and other chemicals suspended in it. That isn't to say plasma is unimportant, however. It is anything but. Antibodies, clotting factors, and other constituent parts can be separated out and used in concentrated form to treat autoimmune diseases or hemophilia—and that is a huge business. In the United States, plasma sales make up 1.6 percent of all goods exported, more than America earns from the sale of airplanes.

Red blood cells (formally called erythrocytes) are the next most plentiful component, constituting about 44 percent of the total volume of the blood. Red blood cells are exquisitely designed to do one job: deliver oxygen. They are very small but superabundant. A teaspoon of human blood contains about twenty-five billion red blood cells, and each one of those twenty-five billion contains 250,000 molecules of hemoglobin, the protein to which oxygen willingly clings. Red blood cells are biconcave in shape—that is, disk shaped but pinched in the middle on both sides which gives them the largest possible surface area. To make themselves maximally efficient, they have jettisoned virtually all the components of a conventional cell—DNA, RNA, mitochondria, Golgi apparatus, enzymes of every description. A full red blood cell is almost entirely hemoglobin. It is essentially a shipping container. A notable paradox of red blood cells is that although they carry oxygen to all the other cells of the body, they don't use oxygen themselves. They use glucose for their own energy needs.

Excerpted from The Body by Bill Bryson. Copyright © 2019 by Bill Bryson. All rights reserved. No part of this excerpt may be reproduced or reprinted without permission in writing from the publisher.