The muscularis externa is a layer of muscle found in the walls of various organs in the digestive tract, such as the esophagus, stomach, and intestines. It typically consists of two layers: an inner circular layer and an outer longitudinal layer. These muscle layers work together to facilitate the movement of food through the digestive system by contracting and relaxing in a coordinated manner. This layer is crucial for the process of peristalsis, which is the rhythmic contraction that pushes food along the digestive tract. The muscularis externa also plays a role in mixing food with digestive juices, enhancing the breakdown and absorption of nutrients.