Limakalvojen

Limakalvojen are mucous membranes, moist linings that cover internal surfaces of the body that open to the outside or to body cavities, including the gastrointestinal, respiratory, urogenital tracts and the conjunctiva. They function as barriers, secretory surfaces and immune interfaces.

Structure and secretions. Mucosa typically comprises an epithelium, an underlying lamina propria, and often a thin muscularis mucosae. The epithelium varies by site: stratified squamous in mouth and esophagus for protection; simple columnar in the intestine and stomach for absorption and secretion; ciliated pseudostratified in much of the respiratory tract for mucus transport. Goblet cells and submucosal glands produce mucus, a gel rich in glycoproteins and water that hydrates, traps particles and pathogens, and reduces friction.

Protection and immunity. Mucus forms a physical barrier and contains antimicrobial molecules (e.g., lysozyme, lactoferrin, defensins) and secretory IgA that neutralize pathogens and toxins. Ciliary action and peristalsis clear mucus and trapped material. Mucosal-associated lymphoid tissue in the lamina propria coordinates local immune responses.

Health and disease. Integrity and proper secretion are essential; disturbances cause dryness, ulceration or inflammation. Examples include atrophic gastritis with reduced mucus and acid dysregulation, mucositis from radiation or chemotherapy, bacterial overgrowth with thick mucus, conjunctival dryness (dry eye), and infections such as candidiasis or certain viral rhinitis. Cigarette smoke, dehydration and some medications can impair mucus clearance or quality. Healing involves epithelial regeneration and mucus reconstitution.