Which components constitute the mucosa layer of the gastrointestinal tract from lumen inward?

• A. Lamina propria, muscularis mucosae, submucosa
• B. Submucosa, muscularis mucosae, epithelium
• C. Epithelium, lamina propria, muscularis mucosae
• D. Epithelium, lamina propria, muscularis externa

Answer: (C)

The mucosa is the inner lining of the GI tract and consists of three components in contact with the lumen: an epithelial layer that lines the space, a connective tissue layer called the lamina propria, and a thin smooth muscle sheet called the muscularis mucosae that helps create minor movements within the mucosa. Beneath this lies the submucosa, a deeper layer with larger vessels and nerves, and farther out is the muscularis externa, the thicker muscle layers responsible for peristalsis. Because the mucosa is made up of epithelium, lamina propria, and muscularis mucosae, that set is the correct description. The other options mix in layers from outside the mucosa, which belong to deeper wall regions.