system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why does bowel tissue fuse with skin in an ostomy, when it otherwise normally keeps to itself?

My brother has a bowel ostomy, and the edges of his bowel (which have been brought out to the surface of his abdomen) seem to have grown into (ie fused) with the skin around the ostomy opening. Yet internally the bowel doesn't fuse with all the other stuff in the abdomen.
gpt
Actually the organs can 'fuse' to other organs within the abdomen. It's called an adhesion. Surgeons commonly encounter that during hysterectomies, where the fallopian tubes have to be separated from other structures during removal. 

However, the intestines are covered by a loose, apron-like layer of fat, called the greater omentum, that protects the bowel and separates it from the inside of the abdominal wall. 

In the case of your brother's ostomy, as another commenter said, you have two cut areas that are brought together to heal, and the body being what it is, closes off the gap and forms scar tissue that adheres the different types of tissue together.