Which layer of the digestive tract controls digestive propulsion?

Out of the following given choices;

mucosa

serosa

submucosa

muscularis externa

The answer is muscularis externa. This layer is one of the 4 layers (tunics) of the GI tract. It is found beneath the submucosa and is composed of smooth muscles. The smooth muscles are responsible for the involuntary movements called peristalsis, that move food along the gastrointestinal tract.