Characteristics: Divided into 4 layers: mucosa, submucosa, muscularis externa and serosa. The mucosa is the innermost layer of the gastrointestinal tract that is surrounding the lumen, or space within the tube. This layer comes in direct contact with food (or bolus), and is responsible for absorption and secretion. Mucosa is further divided into epithelium, lamina propia and muscularis mucosae.
Function: Submucosa consists of a dense irregular layer of CT with large blood vessels, lymphatic, and nerves. Muscularis externa consists of an inner circular layer and a longitudinal outer muscular layer. Adventitia consists of several layers of epithelia.
Location: Large Intestine.