Which layer houses Auerbach's (myenteric) plexus and what is its primary function?

• A. Submucosa; regulates secretion and local blood flow
• B. Muscularis externa; regulates GI motility
• C. Serosa; protects
• D. Lamina propria; absorption

Answer: (B)

The main concept is where the enteric nervous system networks sit and what they do. Auerbach’s (myenteric) plexus is located in the muscularis externa, specifically between the inner circular muscle layer and the outer longitudinal muscle layer. Its primary job is to regulate GI motility by coordinating smooth muscle contractions, helping generate peristaltic waves and segmental movements to move and mix contents.

In contrast, the submucosal (Meissner’s) plexus resides in the submucosa and mainly modulates secretion and local blood flow. The serosa is the outer protective covering, and the lamina propria is the connective tissue within the mucosa that supports it and contains vessels.