Bulging mesothelial cells of the visceral pleura of the rat mimic the network of subpleural lymphatics.

The mesothelial surface of the visceral pleura of the Wistar rat was viewed at high resolution by scanning electron microscopy (SEM). The pleural surface showed exquisite linear arrangements made up of bulging mesothelial cells. They were organized in irregular circles that often presented anastomotic junctures. This arrangement of pleural mesothelial cells mimics the organization of subpleural lymphatics of the lung. A low density of microvilli was seen inside the irregular circles, contrasting with the microvilli-rich mesothelial cells seen on or outside these arrangements. These SEM features of the mesothelium may be related with the formation of microdomains for fluid absorption across the visceral pleura into subpleural lymphatics.