This micrograph of the stomach provides an overview of the structural layers, or tunics, that are associated with the walls of the entire alimentary_canal (GI tract). There are four tunics, and they are (in order from inside to outside) the:
(1) mucosa, which is also called the mucous membrane;
(3) muscularis_externa, and
Each section of the GI tract has these tunics, and each section has unique specializations associated with these tunics. For example, the submucosa of the duodenum, which is the first section of the small intestine, contains duodenal (Brunners) glands. The submucosa of the ileum, which is the last section of the small intestine, contains numerous and obvious lymphoid nodules (Peyers_patches).
The mucosa of each section of the GI tract includes the epithelial surface, lamina_propria and a thin bottom layer (muscularis_mucosae) composed of smooth muscle fibers, which is the border between the mucosal and submucosal layers. In the stomach there are gastric_pits, which are the deep areas positioned between the protruding sections of epithelium, and gastric_glands, which are associated with gastric pits.