Digestive tract: histological organization and function

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Discussing the histological organization of the digestive tract with its function is best down starting with the esophagus and working proximal to distal. The esophagus itself is composed of a mucosa, submucosa, muscularis propria and adventitia. These layers make up most of the GI tract in general, but both the histologic characteristics and the amount of each of these layers varies based on function. The esophagus mucosa is composed of nonkeratinizing stratified squamous epithelial layer that contains a small amount of specialized cells, such as melanocytes, endocrine cells and Langerhans cells. The submucosa consists of loose connective tissues containing blood vessels, a rich network of lymphatics, nerve fibers and some glands. These glands function as accessory salivary glands, to allow for lubricated swallowing. The muscularis propria (site of most of the muscle fibers) is the outmost layer before the adventitia and contains skeletal muscles for the first 6-8cm of the esophagus, then is replaced by smooth muscle. In this way, swallowing is initially continuous with the mouth, and then controlled by smooth muscle.

The stomach is significantly more complicated, as it is largely the initial site of digestion (much of the mastication and some chemical digestion starts in the mouth). As such, it has a much more diverse histology that has varied glandular structures. It also has a mucosa, submucosa, muscularis propria and serosa. Surface area of the stomach is increased significantly through small folds, or rugae, which are ...