Why Is Scar Tissue Different To Normal Skin? - BBC Future

A scar tells the world of injuries past – but why does scar tissue look and feel so different? BBC Future investigates.

When I was 10 or 11 years old, I hurt my knee at summer camp when I fell running around a gravel-covered walkway with some of my bunkmates. I fell hard enough that a few tiny pieces of gravel actually embedded themselves under the skin that covered my kneecap.

In the infirmary, after the nurses wiped away the blood and washed the gravel bits out of the skin, they placed a bucket under my leg and poured rubbing alcohol over it. It hurt, but at least I didn't get an infection. What I did get, however, was a nice scar. Then there was the time I stabbed my hand with a knife while attempting to open boxes in my college dorm room. Despite my best efforts, that, too, resulted in a scar on my left hand, in the space between my thumb and first finger.

Nearly everyone has a good scar story (or two, or three) they can tell in an effort to one-up their friends' stories. But what exactly is scar tissue anyway?

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For one thing, a scar is a virtual certainty following a wound of any sort, at least to some degree. That's because a scar is the natural outcome of the body's normal healing process as it works to repair the skin or another of its organs. However, animals that regenerate parts of their bodies, like limbs or tails, can do this without scarring.

After a wound, burn, or injury, the first thing the body does is bleed. The second thing the body does is form a blood clot. The very top layers of the clot dry out and harden to form a scab, which protects the wound from additional disturbances. Protected from the external world, the lower portion of the clot becomes host to cells called fibroblasts, whose job in part is to replace the scab with scar tissue.