The mesothelium forms a monolayer of flattened squamous-like epithelial cells resting on a thin basement membrane supported by dense irregular connective tissue.

Cuboidal mesothelial cells may be found at areas of injury, the milky spots of the omentum, and the peritoneal side of the diaphragm overlaying the lymphatic lacunae.

The proteins and serosal fluid trapped by the microvilli provide a slippery surface for internal organs to slide past one another.

The main purpose of these cells is to produce a lubricating fluid that is released between layers,[4] providing a slippery, non-adhesive, and protective surface to facilitate intracoelomic movement.

The mesothelium is also implicated in the transport and movement of fluid and particulate matter across the serosal cavities, leukocyte migration in response to inflammatory mediators, synthesis of pro-inflammatory cytokines, growth factors, and extracellular matrix proteins to aid in serosal repair, and the release of factors to promote the disposition and clearance of fibrin (such as plasminogen).