**Core Concept**
The everted edge seen in ulcers is a characteristic feature of certain types of ulcers. This phenomenon occurs due to the contraction of the muscularis mucosae and the submucosa, which pushes the mucosal edge outward. The everted edge is a result of the body's attempt to contain the ulcer and prevent further bleeding.

**Why the Correct Answer is Right**
The everted edge is typically seen in peptic ulcers, particularly those caused by Helicobacter pylori infection. The contraction of the muscularis mucosae and the submucosa is thought to be mediated by the release of histamine and other inflammatory mediators. This process helps to reduce blood loss and promote healing of the ulcer.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is not relevant to the everted edge seen in ulcers. Crohn's disease is a type of inflammatory bowel disease that can cause ulcers, but it does not typically result in an everted edge.
**Option B:** Gastric cancer can cause ulcers, but it does not typically result in an everted edge. The everted edge is more characteristic of peptic ulcers.
**Option C:** This option is not relevant to the everted edge seen in ulcers. Ulcerative colitis is a type of inflammatory bowel disease that can cause ulcers in the colon, but it does not typically result in an everted edge.

**Clinical Pearl / High-Yield Fact**
When examining a patient with a peptic ulcer, look for an everted edge as a characteristic feature. This can help differentiate peptic ulcers from other types of ulcers, such as those caused by gastric cancer or Crohn's disease.

**Correct Answer: D.**