darmwand

Darmwand is the wall of the gastrointestinal tract, typically referring to the intestines. It consists of four principal layers: the mucosa, submucosa, muscularis externa, and serosa or adventitia. These layers work together to protect, absorb, secrete, and propel intestinal contents.

The mucosa is the innermost layer and includes an epithelium, a lamina propria of connective tissue, and a thin muscularis mucosae. In the small intestine the mucosa forms villi and microvilli to increase surface area for nutrient absorption; in the large intestine the surface is flatter and goblet cells secrete mucus to lubricate and protect the lining. The mucosa also contains specialized cells such as enteroendocrine cells and, in the small intestine, Paneth cells.

Beneath the mucosa lies the submucosa, a connective tissue layer that houses blood vessels, lymphatics, nerves, and often glands in certain segments. It contains the submucosal (Meissner) plexus, part of the enteric nervous system that regulates local secretions and blood flow.

The muscularis externa consists of an inner circular and an outer longitudinal muscle layer, responsible for peristaltic movement and segmentation. Between these muscle layers is the myenteric (Auerbach) plexus, another component of the enteric nervous system, which coordinates motility.

The outermost layer is the serosa in intraperitoneal sections or adventitia in retroperitoneal regions. Blood supply comes from branches of the celiac trunk and mesenteric arteries, with venous drainage to the portal circulation and lymphatic vessels including lacteals in the mucosa.

Functionally, the darmwand acts as a selective barrier, enables nutrient and water absorption, secretes mucus and enzymes, and supports gut immunity through gut-associated lymphoid tissue. Pathologies can involve any layer, including inflammatory, ischemic, infectious, or neoplastic processes.