Quote:
Originally Posted by JoeP
Dear Lone Ranger:
Talking about wounds and histamine making blood vessels dilate, what's the reason for inflammation in general? It seems like the benefits of getting more blood to the wound, joint, or diseased area are outweighed both by the psychological impact of the pain and the long-term (oxidant?) damage caused by chronic inflammation.
Yours,
Inflamed* of Johannesburg
* Metaphorically only
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Unpleasant as inflammation is, we'd have rather shorter life expectancies if it weren't for inflammation.
Inflammation is all about increasing blood flow to the site of an injury. This has the immediate effect of causing it to bleed. That's absolutely important. A wound, especially a puncture wound, provides an ideal means of entry into the body by bacteria, viruses and parasites. The initial bleeding of a wound helps to clean it out and drastically reduces the likelihood of bacteria, etc. getting into the general circulation, where they could do tremendous damage.
Because blood flows
into the site of injury faster than it flows out, and because the capillaries in the injury site become porous and so leak fluid, there is swelling. It actually works rather well to isolate the site of injury, making it very difficult for bacteria, etc. to get out of the injury site and into the general circulation.
There are several other important components to the inflammatory response. The increased flow of blood to the area of injury brings in
complement proteins and
antibodies that help fight infection. The increased blood flow also brings in
neutrophils and other white blood cells that help to fight infection. The increased porosity of the capillaries makes it easier for
macrophages and other specialized white blood cells to move into the injury site, where they'll destroy bacteria and damaged or dead body cells.
The release of histamines and other chemicals by affected tissues not only stimulates inflammation, but also helps to attract white blood cells to the injury site.
Another reason inflammation is a good thing is that the increased flow of blood to the injury site causes the temperature of the area to rise. (The blood coming from the interior of the body is warmer than is blood in the outer portions of the body, so increasing blood flow to an injury site will cause it to heat up.) Increasing the temperature by just a few degrees increases the metabolic rate of (surviving) cells, speeding the repair of injured tissues and increasing the efficiency with which the various white blood cells can function to dispatch invaders. Also, many bacteria are quite temperature-sensitive, and raising the temperature of damaged tissues by just a few degrees can seriously slow down bacterial reproduction, giving the body's defenses a better chance of fighting off the infection.
The fact that inflamed tissue is so painful is probably adaptive, too. The very fact that inflammation is so painful encourages us
not to put any pressure on an injury site or to otherwise use it. That reduces the chance of further injury, speeds healing time, and reduces the chance that pressure on the injury site might force pathogens into the general circulation.
So, while the inflammatory response is most-definitely unpleasant, it's definitely a good thing.
Cheers,
Michael