What makes the anatomy of the stomach wall unique compared to the other parts of the digestive system?

The three muscle layers in the stomach's mascularis externa.

Explanation:

The stomach has four layers in their wall; The mucosa which is the inner lining of the stomach that secretes hydrochloric acid. The submucosa made of connective tissues, nerve fibres and blood vessels. The mascularis externa, made of 3 muscle layers responsible for contraction and parastalsis. The outer fibrous membrane or layer called serose.

The muscularis externa in the stomach is unique in that it has three muscle layers compared to the rest of the gastrointestinal tract. This is because the stomach has to work extra hard in mechanically breaking down chunks of food into smaller pieces during digestion.