AP BIOLOGY

Detailed explanation-1: -The GI tract contains four layers: the innermost layer is the mucosa, underneath this is the submucosa, followed by the muscularis propria and finally, the outermost layer-the adventitia . The structure of these layers varies, in different regions of the digestive system, depending on their function.

Detailed explanation-2: -The mucosa, or mucous membrane layer, is the innermost tunic of the wall. It lines the lumen of the digestive tract. The mucosa consists of epithelium, an underlying loose connective tissue layer called lamina propria, and a thin layer of smooth muscle called the muscularis mucosa.

Detailed explanation-3: -Mucosa has three layers: epithelium, lamina propria and muscularis mucosae. It plays an important part in immunity.

Detailed explanation-4: -Complete answer: Digestive mucosa is made up of three sublayers and the Innermost layer of the mucosa is made up of columnar epithelium except in the mouth, esophagus, and anus where it’s stratified squamous. Hence the Innermost layer of the mucosa is made up of columnar epithelium except for Oesophagus.