Pleurae

Anatomy

Each pleura comprises a superficial serosa made of a simple monolayer of flat (squamous) or cuboidal mesothelial cells with microvilli up to 6 μm (0.00024 in) long. The mesothelium is without basement membrane, and supported by a well-vascularized underlying loose connective tissue containing two poorly defined layers of elastin-rich laminae. The costal parietal pleurae also have adipocytes in the subserosa, which present as subpleural/extrapleural fats and are histologically considered belonging to the endothoracic fascia that separates the subserosa from the inner periosteum of the ribs. Both pleurae are quite firmly attached to their underlying structures, and are usually covered by surface glycocalyces that limit fluid loss and reduce friction.