Mucosal

Mucosal refers to mucous membranes, the thin tissues that line cavities and passages that open to the outside of the body, including the mouth, nose, airways, digestive tract, urinary tract, and the front of the eye. These membranes consist of an epithelial layer lying on a lamina propria, often with a muscularis mucosae.

The epithelium varies by site, being simple or stratified as needed for protection and secretion. Goblet cells and mucous glands produce mucus, which lubricates surfaces, traps microbes, and interfaces with the underlying immune system. Mucus also helps regulate the movement of contents and acts as a barrier to pathogens.

Immune defense at mucosal surfaces is organized as mucosa-associated lymphoid tissue (MALT). Secretory IgA antibodies, antimicrobial peptides, and resident immune cells cooperate to prevent infection while preserving tolerance to non-pathogenic substances. The mucosal barrier also relies on physical mechanisms such as cilia, tight junctions, and rapid epithelial turnover.

Organ-specific features include the respiratory mucosa with ciliated epithelium; the intestinal mucosa bearing villi and microvilli for absorption; the conjunctival mucosa of the eye; and the uro-genital mucosa, which adapts to distension and flow. Mucosal damage or inflammation can disrupt barrier function and mucus production, contributing to conditions such as mucositis or inflammatory bowel disease.

Mucosal health is important in vaccine delivery and in understanding pathogen entry. Studies of mucosal immunology inform therapies and preventive strategies that target these surfaces.