Final answer:
The mucosa of the GI tract consists of three layers: the epithelium, the lamina propria, and the muscularis mucosae, and it is one of four total layers making up the wall of the GI tract.
Step-by-step explanation:
The mucosa of the gastrointestinal (GI) tract usually consists of three layers. The innermost layer surrounding the lumen, or the open space within the organs of the GI tract, is primarily made up of epithelial cells, which have the ability to secrete and absorb substances such as digestive enzymes, mucus, nutrients, and water. The mucosa is just one of the four total layers that make up the wall of the GI tract, with the others being the submucosa, muscularis externa, and serosa, but the mucosa itself consists of three subdivisions: the epithelium, the lamina propria, and the muscularis mucosae.