MadSci Network: Medicine

Re: Why does scar tissue slowly disappear?

Date: Fri Jul 31 06:37:18 1998
Posted By: Michael Martin-Smith, Other (pls. specify below), Family Physician, Fellow,BIS, amateur astronomer( BAA), British Interplanetary Society
Area of science: Medicine
ID: 895602881.Me

Healing of wounds, internal and external, takes place by a quick ( 
plugging the leaks, and clearing debris/dead tissue, dirt or invading 
pathogens) and a slow stage ( definitive repair and restoration of 
longterm durable integrity to the damaged surface tissues). 
 THis is rather like a household plumbing repair; first, you turn the 
taps off or plug the leak, then you go to find the source of the problem 
and replace the deamaged pipe/pumps/valves etc which are ultimately 
	The quick stage involves increased supply of blood,local blood 
vessels, antibodies and  clotting materials, and white cells to fight 
local bacterial invaders; this results in a local clot, which scabs 
over, in a few days. If there is infection or dirt, the white cells 
predominate, and there is more flow of blood and serum, and 
inflammation, causing pus formation, which can well delay matters. This 
is the emergency repair phase. 
	The slower, more definitive phase involves migration by newly 
regenerated tissues, which, if the wound is slight and clean, can lead 
to virtually no scarring. If the gap from the injury is too wide, the  
tissues form a scaffolding of collagen fibres across the scab, and the 
result is a scar, which slowly contracts. This scar tissue has no blood 
supply, and so is effectively biologically inert like hair or toe nail! 
	However, over very long times, local phagocytes( scavenging 
cells) might be able to nibble away at the edges of scar tissue, 
allowing for a slow replacement by underlying active tissues, like skin 
or membranes. Because a scar forms an effective repair, replacement is 
not a high priority, as long as surface integrity has been achieved, and 
since, as I have said, scar is inert, bloodless tissue, removal would be 
very slow from the margins, and often, if the scar is substantial, does 
not happen at all. The tendency of scars to turn pale after initial 
inflammation shows the withdrawal of active attempts by the body to 
repair further, which is why most scars go pale and shrink to some 
extent. Similar principles operate internally
	 In the case of tissues which do not readily regenerate, like 
nervous tissues, scars form permanently in default of new nerves.
 Michael Martin-Smith

Michael Martin-Smith

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