The muscularis mucosae is a thin layer of smooth muscle found in the gastrointestinal tract, specifically within the mucosa layer. It plays a crucial role in facilitating the movement of the mucosal layer, helping to enhance the absorption and secretion processes in organs like the stomach and intestines. This layer is located just beneath the lamina propria, which is a connective tissue layer. The contraction of the muscularis mucosae allows for localized movements, aiding in the mixing of contents and the expulsion of secretions from glands in the mucosa.