Scar tissue in the uterus is essentially the same as scar tissue anywhere else in the body, such as a scar from a deep cut on the arm. Doctors actually use many different words for scar tissue depending on what part of the body they’re talking about, such as “adhesions,” “synechiae,” “fibrosis,” or “scar.” But they all are essentially the same thing: a very tough, watertight, non-elastic tissue that acts like permanent superglue. 

Whenever the body is wounded, lots of chemical alarms are activated. Some of them trigger a blood clot right away; other alarms activate lots and lots of fibroblasts, which start the process of long-term healing by creating a scar. Fibroblasts act like “Spiderman” because they send out thin fibers in all directions, bridging any gaps they can find. When these fibers stick to something, the fibroblasts steadily pull on the ends, trying to bring everything together into a small, tightly woven package. At the same time, the fibroblasts are making the web thicker, stronger and reinforced with new fibers. They also send out chemical signals that attract still more fibroblasts, plus new blood vessels that grow into the scar. In the end, where there used to be a space or gap between edges of a wound (or between any two tissues), all that is left is a tightly woven, densely packed net of very tough fibers with its own blood supply. The other problem with scar tissue is that when it’s cut, it desperately tries to regrow itself; once established it can be extremely difficult to get rid of it. If we’re talking about a cut on the outside of the body, this is a good thing. If we’re talking about the inside of the uterus, it’s very unfortunate. 

What happens with Asherman’s Syndrome is that after uterine endometrium has been lost (for example, if it was completely scraped away during a D&C), the exposed layers of the uterus wall underneath are literally raw and wounded. When the uterus tries to heal itself, it doesn't understand that all it needs would be to regrow a new endometrium; it reacts exactly as if it were a cut muscle in the leg or arm or anywhere else. The result is that fibroblasts weave a web across the uterine cavity and tighten everything down into a thin but extremely strong layer of scar. In the worst case, the entire uterine cavity can be completely gone, leaving behind a uterus that now resembles a solid muscular ball with a scar down the middle.