Sidekalvon

Sidekalvo, commonly known in English as the serous membrane or serosa, is a thin, smooth membrane that lines closed body cavities and covers the external surfaces of most visceral organs within those cavities. It consists of a layer of simple squamous epithelial cells called mesothelium, supported by a thin layer of connective tissue, and it secretes a lubricating serous fluid.

The serous membrane forms two layers: a parietal layer that lines the cavity walls and a visceral layer that covers the organs within the cavity. The two layers are continuous at the edges of the cavities and are separated by a potential space filled with serous fluid, which reduces friction during organ movement.

Serous membranes exist in several major body cavities, including the pleura around the lungs, the pericardium around the heart, and the peritoneum lining the abdominal cavity and covering abdominal organs. Some organs have serosal surfaces as they contact these cavities.

Functions include providing a friction-reducing lubricating surface, separating organs to limit the spread of infections, and contributing to immune defense via resident mesothelial cells and underlying tissue.

Clinical relevance: inflammation of serous membranes (serositis) can cause pleuritis, pericarditis, or peritonitis; excess fluid accumulation in the serous spaces leads to effusions or ascites.

Developmentally, serous membranes arise from the mesoderm in embryogenesis, forming the parietal and visceral layers that enclose and protect organs.