In order, starting with the innermost layer, what are the four walls of the digestive tract?

The correct sequence of the layers of the digestive tract, starting with the innermost layer, is indeed mucosa, submucosa, muscle (also referred to as the muscularis externa), and then serosa or adventitia on the outside.

The mucosa is the innermost layer, consisting of epithelial cells that provide a barrier and secrete mucus and digestive enzymes. Surrounding the mucosa is the submucosa, which contains connective tissue, blood vessels, and nerves that support the mucosa. The muscularis layer follows, composed of smooth muscle, which facilitates the movement of food through the digestive tract by performing peristalsis. Finally, the outermost layer is the serosa, a smooth membrane that reduces friction between adjacent organs within the abdominal cavity.

Understanding this order is crucial for healthcare professionals, particularly when coding medical procedures or diagnosing conditions related to the gastrointestinal system. Recognizing how these layers interact and function is fundamental knowledge in anatomy and physiology, which directly applies to understanding diseases that may affect these structures.