Peristaltic activity in the muscularis externa is regulated by the enteric nervous system and the autonomic nervous system.This helps churn the chyme in the stomach. The stomach has a third layer of muscularis externa: the inner oblique layer.In the colon, the muscularis externa is much thicker because the feces are large and heavy, requiring more force to push along.Between the two muscle layers is the myenteric or Auerbach’s plexus, which controls peristalsis.The coordinated contractions of these layers is called peristalsis, which propels the food through the GI tract. The muscularis, or muscularis externa, consists of an inner circular muscular layer and a longitudinal outer muscular layer.The submucosa lies under the mucosa and consists of fibrous connective tissue, separating the mucosa from the next layer, the muscularis externa. The submucosa also has glands and nerve plexuses. The absorbed elements that pass through the mucosa are picked up from the blood vessels of the submucosa. The submucosa is relatively thick, highly vascular, and serves the mucosa. Each layer has different tissues and functions. nerve: A bundle of neurons with their connective tissue sheaths, blood vessels, and lymphatics.lymphatic: The system that carries a clear fluid called lymph that is formed from interstitial fluid collected through the capillaries.parasympathetic ganglia: The autonomic ganglia of the parasympathetic nervous system they lie near or within (respectively) the organs they innervate.Tiny parasympathetic ganglia are scattered around to form the submucosal plexus (or Meissner’s plexus) where preganglionic parasympathetic neurons create synapses with postganglionic nerve fibers that supply the muscularis mucosae.In the gastrointestinal tract, the submucosa is the layer of dense, irregular connective tissue or loose connective tissue that supports the mucosa, as well as joins the mucosa to the bulk of underlying smooth muscle (fibers that run circularly within a layer of longitudinal muscle).The absorbed elements that pass through the mucosa are picked up from the blood vessels of the submucosa.In the small intestine, the epithelium (particularly the ileum) is specialized for absorption, with villi and microvilli increasing surface area.the epithelium is simple columnar, and is organized into gastric pits and glands to deal with secretion. In the esophagus, the epithelium is stratified, squamous, and non-keratinizing, for protective purposes.The most variation is seen in the epithelium tissue layer of the mucosa. The mucosae (singular: mucosa) are highly specialized in each organ of the gastrointestinal tract in order to deal with different digestive tract conditions. The muscularis mucosae is a thin layer of smooth muscle and its function is still under debate.The lamina propria is a layer of connective tissue that is unusually cellular compared to most connective tissue.The epithelium is the innermost layer and it is responsible for most digestive, absorptive, and secretory processes.General structure of the gut wall: This cross section shows the mucosa in relation to the interior space, or lumen. Food, mucus, and digestive juices pass through the lumen, and the mucosa comes in direct contact with digested food (chyme). Since the mucosa is the innermost layer within the GI tract, it surrounds an open space known as the lumen. Layers of GI tissue: Note the mucosa, located at the innermost layer. On the mucosa layer, small finger-like projections called villi and microvilli help to increase surface area for nutrient absorption. The mucosa contains specialized goblet cells that secrete sticky mucus throughout the GI tract. It is composed of epithelium cells and a thin connective tissue. The mucosa is the innermost layer, and functions in absorption and secretion. From the inside out they are called: mucosa, submucosa, muscularis, and serosa. lumen: The inside space of a tubular structure, such as an artery or intestine.The epithelium of the mucosa is particularly specialized, depending on the portion of the digestive system.This layer comes in direct contact with digested food (chyme).
The mucosa surrounds the lumen, or open space within the digestive tube.
It is made up of three layers: the epithelium, lamina propria, and muscularis mucosae.
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