Stratified squamous epithelium lines the esophagus. Outside the epithelial layer, which is where most cell mitosis in the esophagus occurs, is a layer of loose, slick connective tissue which is home to submucosal glands and other structures important to maintaining the health and structural of the esophagus as it swallows materials.
Below the mucosa is the muscularis mucosa, tracts of smooth, thin muscle fibers which together with the epithelial layer and the connective tissue comprises the mucosa in its entirety. Outside this is the submucosa where glands produce the mucous that keeps the esophagus lubricated. This process allows matter to slide easily down the esophagus without choking the swallower.
The esophagus is the channel by which food, and thus nutrients, enters the human body. To facilitate this process it must be capable of strong muscular action, the process of swallowing, and it must be lubricated and slick at all times. This is why the body's production of mucous in the mouth and esophagus is so crucial to survival.
The esophagus is a complex part of the body with many cooperative layers which perform different functions. Taken together the muscularis mucosa, the submucosa, and the connective tissue create a vital structure which renews itself regularly through mitosis in order to keep the body nourished.