What are the three layers of the muscularis externa in the stomach wall, and how does the oblique layer contribute to stomach function?

The stomach's muscularis externa contains the usual outer longitudinal and middle circular layers of smooth muscle, plus an incomplete inner layer of oblique smooth muscle fibers. The oblique layer helps the stomach pummel and physically break down food by jackknifing the stomach into a V shape, which provides propulsive action in the pyloric region and ram food into the small intestine.

In the stomach wall, the muscularis externa has three layers of smooth muscle: the outer longitudinal layer, the middle circular layer, and an incomplete innermost oblique layer. The circular and longitudinal layers mix, churn, and move food along the digestive tract. The oblique layer adds a pummeling action that breaks food into smaller fragments and helps ram the food toward the small intestine. Specifically, the oblique fibers achieve this by jackknifing the stomach into a V shape, creating a propulsive force in the pyloric part of the stomach.