Layers of Digestive Tract
MUCOSA: Innermost layer of digestive tract. It is also made up of Epithelial layer, Lamina Propria and Muscularis mucosae.
- Epithelial layer makes direct contact with tract and secrete mucus and fluid into the lumen of the tract.
- Lamina propria contains blood and lymph vessels and Mucosa-Associated Lymphatic Tissue (MALT). MALT contains immune cells that protect against disease. It is present all along the GI tract, especially in the tonsils, small intestine, appendix, and large intestine.
- Muscularis mucosae help increase the small folds of the mucosa of Stomach and Small Intestine, which increase the surface area for digestion and absorption.
SUBMUCOSA: It is present outside of mucosa and is made up of loose connective tissue.
- Contains blood and lymph vessels and an extensive network of neurons known as the Submucosal Plexus (Plexus of Meissner).
- Gives the digestive tract its elasticity and its ability to distend.
MUSCULARIS: Outer to Submucosa is Muscularis, formed by smooth muscle layers which form inner Circular layer and outer longitudinal layer.
- Helps in breakdown of food, through the involuntary contractions of the circular and longitudinal muscle, mix it with digestive secretions, and propel it along the tract.
- There is another plexus of neurons present between the layers of the Muscularis, called as Myenteric Plexus (Plexus of Auerbach).
SEROSA: Outermost/superficial layer and is made up of a thin mesothelium (epithelium of visceral organs) with some connective tissues, also called the visceral peritoneum.
- The outermost layer of esophagus is Adventitia, as esophagus lacks serosa.
- Serosa is a serous membrane, so it secretes an aqueous, slippery fluid which lubricates the areas between the digestive organs and other organs, reducing friction between them as they move together as a result of muscle movement.
NOTE: Peritoneum is the largest serous membrane of the body. Peritoneum is divided into the Parietal peritoneum, which lines the wall of the abdominal cavity, and the Visceral peritoneum, which covers some of the organs in the cavity and forms their serosa.
- Space between parietal peritoneum and visceral peritoneum is called as Peritoneal cavity, which contains lubricating serous fluid.
Do check next topic in continuation of this, i.e. modifications in layer of digestive tract in stomach and small intestine.