Here’s a snippet from the first chapter of my new book, How Your Child Heals. It picks up at the point where you, the reader, have begun a microscopic voyage to see what an infected splinter looks like from the perspective of inside your child’s body.
Now that you have had the full-sized, outside view of what happened to your son’s finger, it is time for you to go inside to places where the ancient physicians could not go. It is time to take a seat in the audience of the microscopic drama. You are about to make the first of several trips you will make throughout this book in a tiny, imaginary, high-tech vessel. Think of it as a cross between a submarine and an all-terrain vehicle; it can swim in the blood stream or leave the circulation to crawl around between the cells of the body. It is well-equipped with spotlights and spacious windows, allowing you to see what is happening all around you. The dramatic setting for your first foray is the time just before you called the doctor’s office to ask what to do about it.
The blood vessels in the body form an immense, self-contained system that is divided into two halves. We need oxygen to live, and one half of the circulation, the arteries, carries oxygen-rich blood out to all the parts of the body, down to the tiniest places. The other half, the veins, brings oxygen-depleted and carbon dioxide-laden blood back to the lungs to get more oxygen, which we breathe in, and dump the carbon dioxide waste, which we breathe out. The two halves of the circulation join in a microscopic meshwork of vessels called the capillaries. This is where the true business of circulation happens, where oxygen and other important nutrients get delivered to the body’s cells.
The capillary bed of your son’s throbbing finger is the key place to visit as you investigate what is causing all the problems, but to get there you must first get inside his circulation. You need a location where the tiniest of blood vessels are accessible, close to the surface. The lining of the eye is such a place.
Imagine you begin by poising your craft at the base of one of his lower eyelashes. You look over the edge into the wet, shiny world below. Your son momentarily pulls down his lower lid, revealing the pink inner lining of his lower lid, called the conjunctiva. You seize your chance, zip over the edge, and find yourself motoring about in the clear liquid of his tears, nature’s way of keeping our eyeballs moist. Here there are blood vessels close at hand, just below the surface. You slide your craft into the nearest one and then drift along with the stream, ever faster, as it takes you toward the heart.
You do not stay in his heart long, though, because nothing does. The blood rockets out of the heart like a fire hose because the heart pumps an enormous amount of blood very quickly. A typical adult heart, for example, sends out about a gallon and a half of blood every minute, proportionately less in a child. The effect on your vessel is the equivalent of taking a trip over Niagara Falls. You get bounced around, but soon find yourself in the aorta, the large vessel exiting from his heart.
The aorta is wide and fast, but it soon divides, then subdivides, into multiple rounds of ever smaller vessels. As this branching happens, the velocity of the stream in each of them slows down dramatically. Within seconds after leaving his heart you are scooting down one of these tributaries, headed for his painful index finger.
Things were moving so fast in the aorta and the first couple of branchings that you could not see any details in the surrounding walls of the blood vessels. Although you are going slower now, your pace is still a brisk one, and the flow still pulses along–now faster, now slower–in rhythm with your son’s heartbeat. Soon the stream slows down enough for you to get some idea of just what kind of pipe you are traveling through. The first thing you see when you shine a light at the walls is that the surface is covered by a bumpy layer of cobblestone-appearing cells. The junctions between these cells make a completely watertight barrier; no blood can leave this sealed pipe, and thus you cannot see what is going on in the tissues outside of it.
You soon find you are slowing down even further as you come closer to the sore on his finger, and you notice a dramatic change in the walls of the blood-filled passage you are passing down. For one thing, the wall of the tube is now translucent; you can shine your light right through and get a hazy view of what lies beyond. There are now some small gaps between the pavement of flat cells that makes up the walls, but the cells still mostly touch one another along their edges.
You have reached the capillaries. In real life there would be millions upon millions of options for you to have chosen on your trip from the aorta as the tubes branched into ever smaller pathways, but for our purposes we assume your miniature craft has the proper instruments to sense the correct path among the myriad of choices to lead you to the sore spot on your son’s finger.
Sachin on 