Slemlagret

Slemlagret (Swedish for "the mucus layer") is a gel-like biological barrier that coats the surfaces of many organs, notably the respiratory and gastrointestinal tracts, eyes and reproductive organs. It is primarily composed of water, high-molecular-weight glycoproteins called mucins, salts, lipids, antimicrobial peptides and shed epithelial cells. The physical properties of slemlagret—viscosity, elasticity and porosity—are determined by mucin concentration and crosslinking.

Functionally, slemlagret protects underlying epithelia from mechanical damage, dehydration and chemical irritation, and acts as a first-line defense against pathogens by trapping microbes and facilitating their clearance. In the airways it is moved by cilia in the mucociliary escalator; in the gut it forms a selective barrier that permits nutrient exchange while limiting bacterial contact with epithelial cells. In some organs, notably the colon, the mucus exists as two distinct layers: an inner, dense layer that is largely sterile and an outer, looser layer inhabited by commensal bacteria.

Slemlagret is continuously renewed by specialized secretory cells such as goblet cells. Alterations in its composition or thickness are implicated in disease: excessive or thickened mucus contributes to obstruction in cystic fibrosis and chronic bronchitis, while reduced mucus protection is associated with ulceration and inflammatory bowel diseases. Current research explores mucus-microbiome interactions, synthetic mucin analogs and therapies aimed at restoring healthy mucus properties to prevent infection and inflammation.