mucosae

Mucosae, or mucous membranes, are moist linings that enclose body cavities and passages that communicate with the exterior. In most areas they consist of an epithelium supported by a lamina propria of loose connective tissue and a thin layer called the muscularis mucosae. Goblet cells and mucous glands secrete mucus, which protects the tissue, traps particles, and keeps surfaces lubricated.

Different regions have different epithelial types: stratified squamous epithelium lines the oral cavity, esophagus, and portions of the genital tract; simple or pseudostratified columnar epithelium lines much of the respiratory and digestive tracts, often with cilia and absorptive microvilli. The variation supports region-specific secretion, absorption, and protection.

Functions and immunity: mucosae act as a barrier to pathogens, participate in immune defense, and contain mucosa-associated lymphoid tissue (MALT). Secretions include mucus rich in antibodies such as secretory IgA, antimicrobial peptides, and enzymes. The underlying lamina propria hosts immune cells that respond to inhaled or ingested antigens.

Clinical notes: mucosal damage or dysfunction underlies many diseases, including inflammatory bowel disease and ulcers. Mucosal tissues are common sites of infection and are important in mucosal vaccination and drug delivery. The mucosa is distinct from serosa and submucosa, but together with the epithelium and muscularis mucosae forms the mucous membrane.