Why and how is Scar tissue different than the rest of your body’s tissues?
In: Biology
Scar tissue is the body’s way of replacing injured tissue with some, often permanent, filling to maintain structural and limited functional integrity. For example, if you get a cardiac ischemic insult (cut off blood supply to the heart muscle due to a clot or whatever), the tissue in the region may begin to die due to hypoxia (low oxygen). The heart muscle cells (cardiomyocytes) cannot divide in adults, so how do you repair this? You can’t just have one dead region that eventually gets eaten by phagocytes (immune cells that eat debris from dead cells and foreign objects), you’d have a big problem. So the heart instead develops scar tissue in the region, which is simply fibrous tissue made of collagen amongst other things and produced by fibroblasts which reside almost everywhere to keep maintaining the extracellular matrix (the protein network between and around cells). The fibroblasts just keep depositing these proteins to fill in the gap and maintain the structure of the heart. Of course this region is all but functionally useless, it doesn’t contract, it doesn’t conduct electricity to the rest of the heart downstream, etc, and so it does create problems like arrythmias (where the electric waves start going in circles or spreading aberrantly causing a dysregulation in heart rhythm). So it’s a repair mechanism, but a far from perfect one, just a patch it up sort of approach. This stuff happens all over, like in chronic kidney injury where nephron cells start dying, you can’t replace a nephron, it’s simply too complex. Of course in some instances scar tissue is a temporary solution, until real repair kicks in, but that only happens when the tissue itself can rebuild itself, like the liver.
So to answer your question, normal tissues are organized and functionally viable, scar tissue is neither.
Edit: after I read the other comments, I feel like I should clarify that scar tissue doesn’t only refer to what your scars are made of when your wound heals, and the word tissue doesn’t just refer to organized collagen, that’s actually just one subtype, called connective tissue, which has maaaaaany types too. But the word tissue in biology refers to a level of organization that falls between a cell and an organ. It’s essentially a collection of cells that are similar in type, that carry out similar functions, that cooperate together to produce a larger function, and that are housed in a similar environment of extracellular proteins and signals (paracrine signals for example) and other things (pH, vascularization, etc). So organs are made of, usually, multiple tissues, which themselves made of, usually, a population of multiple similar cell types.
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