Structure of the gastrointestinal tract (GIT) is the same from oesophagus to the anus. Mucosa shows variations in different regions of the tract according to the function of the particular part. Gastrointestinal tract shows four layers: 1) Mucous membrane or mucosa is made up of three components: Epithelium: is stratified squamous epithelium (may be either keratinized or nonkeratinized depending on the diet). Lamina propria: is a layer of loose areolar tissue. Muscularis mucosa produces local movement of mucosa. 2) Submucosa: is loose collagenous connective tissue showing blood vessel, lymphatics and nerves, shows submucosal plexus. It also shows oesophageal glands.