Mukosa

Mukosa, also called mucosa or mucous membrane, is a moist tissue lining body cavities and passages that communicate with the exterior. It consists of an epithelial layer resting on a loose connective tissue layer called the lamina propria, and often a thin muscle layer called the muscularis mucosae. Mucosa lines the digestive, respiratory, and urogenital tracts, as well as the oral cavity, nasal passages, portions of the eye, and other specialized regions such as the olfactory mucosa. The epithelium varies by site: stratified squamous in the mouth and esophagus; simple columnar in the stomach and intestines; pseudostratified ciliated columnar in most of the respiratory tract. Goblet cells and other secretory cells produce mucus, which lubricates surfaces and helps trap pathogens. The lamina propria contains blood vessels, nerves, and immune cells, forming mucosa-associated lymphoid tissue (MALT) that contributes to local immune defense. A thin muscularis mucosae can modulate local movement and secretion.

Functions of mucosa include protecting underlying tissues, secreting mucus, enzymes, and hormones, and, in the gastrointestinal tract, absorbing nutrients. In the respiratory tract, mucosa supports mucociliary clearance, helping to remove inhaled particles. Mucosal immunity is a key component of overall immune defense, with specialized lymphoid tissue and secretory IgA playing roles at many sites.

Clinical notes: mucosal surfaces are common sites of infection and inflammation. Mucositis can follow chemotherapy or radiotherapy, and mucosal disorders accompany conditions such as inflammatory bowel disease, celiac disease, and allergic reactions. Etymology derives from Latin mucosa, “mucous membrane.”