GrumpyOldLadyTech t1_iuhryp1 wrote on October 31, 2022 at 1:07 PM

Reply to comment by labdog in eli5 - If our cells only turn a certain amount of times before we die. Does causing micro damage from resistance training shorten our lifespan? by aus_ben93

In theory, and dependant on the tissue involved, repeated trauma has a possibility of giving rise to cancer. The skin is not generally one of these tissues.

The way skin forms is kinda special. It's an epithelial tissue, meaning it's designed to rubbed, bumped, and slid against. The inside of your mouth is epithelial tissue, as are other parts of the digestive system and reproductions system. Even the lining of your urethra is epithelial cells. They're used to the constant minor abuses and have evolved accordingly.

So what's special about it? All your skin is formed in deep tissue called the dermis, by epithelial cells caked basal cells. Think "basal" like "basement," as they are the bottom layer of your skin. Their entire job is to replicate and push more skin cells upward. Those new cells eventually die off as they move upward and become what you know of as your skin. Problems with basal cells are most often caused by radiation damage - like prolonged and repeat exposure to UV - because they replicate so often and so quickly, not from repeat trauma.

Now, if you're cutting the exact same spot on your skin for, like, years? Constantly? Yeah, that's probably not great. But microtears in muscular and epithelial tissue isn't the end of the world. They're used to that, and they're designed to cope.

Edit: I focused on skin, because that's usually what you mean by cuts and scrapes. If you've been frequently cutting into muscle tissue, I'm worried about you for reasons beyond cancer.

labdog t1_iuhy0db wrote on October 31, 2022 at 1:55 PM

Thanks, I've learned a lot. A couple of days ago I had a minor accident and took a little "meat crayon" like damage. A hand skin torn to shreds, an elbow looking like a slightly used meat crayon. I'm amazed how fast it healed. It looks like I have some brand new skin. It silly but when I get similar "paint scratches" I wonder if it heals this time or not. Well, I have a couple of permanent scars from various accidents, but I've heard it's only because it wasn't sewn. It healed naturally and deeper cuts left some scars. I never had a muscle or bone damage. I'm too careful for that. From the other hand - I'm always in a hurry and I use various tools a lot, so that accounts for plenty of minor damages. It's good to know it's nothing to worry about.

GrumpyOldLadyTech t1_iujjddz wrote on October 31, 2022 at 8:23 PM

What you're describing is "second intention" healing: the act of the body healing a wound without closure. It's unnecessary (and sometimes impossible) to suture every wound. Not much to glue together on, say, a skinned knee. Second intention healing actively scars over as fibrin (manufactured by your liver) knits a structure together for cellular regeneration. That's why a scar looks different from your usual skin: it's literally built over a scaffolding that your body isn't made of normally.

It's common and harmless, just letting a wound granulate in. Usually best for superficial wounds like abrasions, though I've seen it with deeper wounds on occasion. In both cases I can think of immediately, the wound was bandaged with honey, which acted as a secondary granular structure while also protecting the deep tissue from infection. Eventually the skin grew back in, though both times it did scar rather spectacularly. The doctors on each case felt sutures would be difficult and risky, based on the mobility of the sites as well as poor "margins," which are the edges of wounds. Without proper margins, they're nothing to really suture. Imagine taking a half-dollar sized patch of skin off your wrist: how do you put the edges back together on such a wide, mobile space? You don't. You let it heal by second intention.

Sutures (and staples) come in to play with lacerations mostly. Nice, deep, linear wounds with most of the skin still available to suture. But that's a different subject.

Your two biggest organs - your skin and your liver - are also the only two with active regenerative properties. That doesn't mean take them for granted, but do have a little trust!