serous membranes

Layers of tissue lining the closed cavities of the body, and characterized by the secretion of a serous fluid; they allow the organ to slide within its cavity.

The serous membranes are the pericardium, around the heart; the two pleurae, around the lungs (pleurisy is an inflammation of these); the peritoneum, around the intestines; and the two tunicae vaginales, around the testes. The membranes consist of two layers, a visceral and a parietal layer, between which is a small amount of serous fluid. Each layer in its turn consists of a lamella of endothelial cells upon a protective coat of fibrous tissue.