Limaskest

Limaskest, commonly referred to as the mucous membrane, is the moist lining that covers many cavities and passages that connect with the outside of the body. It forms a protective barrier and participates in secretion, absorption, and immune defense. The mucous membrane consists of an epithelial surface supported by a lamina propria of loose connective tissue, and in many regions a thin layer of smooth muscle called the muscularis mucosae. Goblet cells and mucous-secreting glands produce mucus that traps particles and supports clearance of trapped material.

Location and variation: Mucous membranes line the respiratory, digestive, urinary, and some reproductive tracts, as well as the conjunctiva of the eye. The type of epithelium varies with function: simple columnar or cuboidal in many digestive organs; pseudostratified ciliated columnar in much of the respiratory tract; stratified squamous in parts exposed to abrasion such as the mouth, esophagus, and vagina.

Functions: They protect against mechanical and chemical injury, mediate exchange of substances through secretion and absorption, and provide immune defense. Goblet cells and mucus trap pathogens; lymphoid tissue in the lamina propria supports local immune responses. Glands may supply additional fluid and enzymes, aiding lubrication and digestion where appropriate.

Clinical relevance: Mucous membranes are commonly affected by infections, inflammation, and autoimmune processes. Inflammation of a mucous membrane is referred to by location, such as rhinitis or gastritis. Barrier dysfunction can contribute to infections and dehydration, and mucosal tissues often regenerate rapidly after injury, aided by resident stem cells in the basal layer.

See also: mucosa, mucous glands, mucociliary clearance, mucosal immunity.