<Ul> <Li> Mucosa </Li> <Li> Submucosa </Li> <Li> Muscular layer </Li> <Li> Serosa (if the tissue is intraperitoneal) / Adventitia (if the tissue is retroperitoneal)--these last two tissue types differ slightly in form and function according to the part of the gastrointestinal tract they belong to (see the section below for more detail) </Li> </Ul> <Li> Serosa (if the tissue is intraperitoneal) / Adventitia (if the tissue is retroperitoneal)--these last two tissue types differ slightly in form and function according to the part of the gastrointestinal tract they belong to (see the section below for more detail) </Li> <P> The epithelium, the most exposed part of the mucosa, is a glandular epithelium with many goblet cells . Goblet cells secrete mucus, which lubricates the passage of food along and protects the intestinal wall from digestive enzymes . In the small intestine, villi are folds of the mucosa that increase the surface area of the intestine . The villi contain a lacteal, a vessel connected to the lymph system that aids in the removal of lipids and tissue fluids . Microvilli are present on the epithelium of a villus and further increase the surface area over which absorption can take place . Numerous intestinal glands as pocket - like invaginations are present in the underlying tissue . In the large intestines, villi are absent and a flat surface with thousands of glands is observed . Underlying the epithelium is the lamina propria, which contains myofibroblasts, blood vessels, nerves, and several different immune cells, and the muscularis mucosa which is a layer of smooth muscle that aids in the action of continued peristalsis and catastalsis along the gut . </P> <P> The submucosa contains nerves including the submucous plexus (Meissner's plexus), blood vessels and elastic fibres with collagen, that stretches with increased capacity but maintains the shape of the intestine . </P>

Layer of digestive tract that contains blood vessels