serous membrane

A serous membrane consists of two layers: the mesothelium — a single layer of flattened epithelial cells that secrete serous fluid — and an underlying connective tissue layer that provides structural support and anchors the membrane. Together, these layers form a smooth, moist surface that reduces friction between moving organs.

The three principal serous membranes in the human body are: the pleura (lining the thoracic cavity and covering the lungs), the pericardium (enclosing the heart), and the peritoneum (lining the abdominal cavity and covering abdominal organs). Each forms a closed sac with parietal and visceral layers separated by a thin film of serous fluid.

Serous membranes can become inflamed or develop excess fluid accumulation. Pleuritis (pleurisy) affects the pleura, pericarditis affects the pericardium, and peritonitis affects the peritoneum — each causing pain and potentially impairing organ function. Malignant mesothelioma is a cancer arising from mesothelial cells, often linked to asbestos exposure.