What inflammation looks like up close and personal, part II

February 6, 2011  |  General

Here’s another snippet from the first chapter of my new book, How Your Child Heals. It’s from the chapter about inflammation, and follows from here. The action picks up at the point where you, the reader, have taken your microscopic voyage to reach the smallest blood vessels in the body — the capillaries.

Before you reach the site of the action itself, though, you pause to look around at what is floating along with you in the bloodstream. It is a crowded thoroughfare because the diameter of the tube has become narrower with each branching of the way. When you were in the aorta and the larger arteries, things were simply shooting along too fast to see anything, but now the flow is more sluggish, and you can easily see your fellow travelers, the blood cells, out the window. Several of these cells are key to understanding how healing works, so this is a good time to look them over and learn a little about what they do.

You easily see there are two principal categories of cells. The vast majority, by a thousand-fold or more, are red disks with a dimple in the middle of each side. These are the red blood cells, and their only job is to carry oxygen. They accomplish this by being stuffed full, nearly to the exclusion of everything else, of a carrier substance called hemoglobin. When hemoglobin is loaded with oxygen it is bright red; when unloaded, it is darker in color. This is why oxygen-rich blood from the arteries is so red, whereas oxygen-depleted blood from the veins is a darker, reddish blue. The red blood cells go endlessly round and round the circulation, picking up fresh oxygen as they pass through the lungs and delivering it to the rest of the body. Healing body parts, such as injured fingers, require lots of oxygen.

Mixed in among the hordes of red blood cells, you see an occasional larger cell float by the window. Some of these are little spheres; others look more like jellyfish. Now that you are traveling slowly enough, you see that there is an especially large number of the jellyfish-type cells drifting languidly along the walls of the tube. Both the small spheres and the jellyfish are members of a family of cells called white blood cells. They are not really white, being more translucent in quality. They got their name mainly because they are not red and, when clumped together in a large mass, look whitish.

The jellyfish cells are called neutrophils. These creatures are moving along with you in particularly large numbers to your son’s sore finger, because they are key actors in the cellular drama of inflammation. Although their walls are translucent, like a real ocean jellyfish, you see that they are filled with dark, granular pellets.

You and the blood cells have now entered the narrowest portion of the capillary meshwork. The passageway here is very tight, being the same diameter of the blood cells or even less, which must squeeze through in places by deforming and squishing their elastic sides. Now that the walls are pressing upon your craft, you can see that, as was the case further back up in the artery, these walls are also made up of cells stretched flat and stitched together along their edges like a quilt. Unlike in the arteries, however, here there are substantial gaps along the seams between the cells. These gaps are small enough that the cells cannot slip though, but some of the fluid part of the blood, the river you are moving in, does seep out.

Then you spy just ahead a strange thing: a neutrophil, one of the jellyfish cells, has attached itself to the wall and is squeezing itself through one of the gaps. Neutrophils can slither and crawl along a surface, scrunching themselves between the tiniest of cracks between cells.

Finally you approach the scene. Your first sign of this is that the passageway walls have swollen back out, enlarged in size. This has created huge gaps in them. In fact, it is now difficult to tell if you are inside the capillary or outside it. The gaps are so big that quite a few red blood cells have floated out through the gaps into the surrounding tissue. There seems to be little distinction between the inside and the outside of the vessel. Since the walls are now as porous as cheesecloth, an even larger amount of the surrounding river of blood passes from the capillary.

What you are seeing from your microscopic window is the cellular basis of why an inflamed finger is red and swollen. Normal tissue does not have any red blood cells in it; they stay in the capillary network. The red cells function like long lines of boxcars laden with oxygen that pass through the capillary bed. As the train lumbers along it unloads its cargo of oxygen, which diffuses the short distance into the surrounding tissues to meet the energy needs of the cells there. Your son’s finger is intensely red on the tip because so many red blood cells have leaked out, leaving their usual track.

The leaky capillaries also show you why his finger is swollen and painful—all that fluid leaving the blood vessels stretches the tissues tight as a drumhead. The pressure inside his fingertip becomes dramatically higher than normal, and the increased pressure pushes on the exquisitely sensitive nerve endings there. The result is pain.

More about what happens next in a later post.

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  1. What inflammation looks like up close and personal, part III | Christopher Johnson M.D. PICU Author

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