Mucosubstances

Mucosubstances is a histological term used to describe the mucous-related constituents found in mucus and mucosal tissues. In this context, they are composed primarily of glycosaminoglycans (acid mucopolysaccharides) and mucoproteins (glycoproteins), which together confer the viscous, gel-like properties of mucus and contribute to the extracellular matrix of mucosal surfaces.

The main components include glycosaminoglycans such as hyaluronic acid, chondroitin sulfate, dermatan sulfate, heparan sulfate, and keratan sulfate. These long, unbranched carbohydrate chains are often sulfated and highly hydrated. Alongside these are neutral mucopolysaccharides and mucoproteins, including mucins, which are highly glycosylated proteins that trap water and pathogens. The combination of these substances forms a hydrated gel that protects, lubricates, and traps particulates on mucosal surfaces.

Mucosubstances are produced by goblet cells and mucous glands within the epithelium, as well as by fibroblasts and other cells in connective tissue. They are distributed throughout mucus-secreting regions such as the respiratory, gastrointestinal, and conjunctival mucosa, and play a key role in barrier function, lubrication, and tissue hydration.

In histology, mucosubstances are often detected with special stains: Alcian blue highlights acidic mucopolysaccharides, periodic acid–Schiff (PAS) stains neutral mucosubstances, and the AB-PAS combination can differentiate both types. Abnormal accumulation or altered composition of mucosubstances is seen in certain metabolic disorders (e.g., mucopolysaccharidoses) and in various pathological states affecting mucosal tissues.