The thickest layer of the stomach is the muscularis externa. This layer is responsible for the churning and mechanical digestion of food. It's made up of three layers of smooth muscle: longitudinal, oblique, and circular. The oblique layer is unique to the stomach and helps to mix food with digestive juices.
The muscularis externa is essential for the stomach's function, and its thickness allows it to generate the strong contractions needed for proper digestion.
