Scanning electron microscopy of the deep lymphatic network of the murine lung as viewed in corrosion casts

The lymphatic microvessels of the deep lung tissue were studied in corrosion casts, which were observed by scanning electron microscopy (SEM) after injection of a methacrylate resin (Mercox) through the trachea of CD-1 mice. We found that the deep lymphatics of the murine lung were composed of two interconnecting networks: a poorly developed capillary system located at the interacinar region, and a rich plexiform complex surrounding the bronchus. Lymphatic capillaries did not penetrate the alveolar area, thus leaving most of the lung parenchyma devoid of direct access to lymphatic drainage. Lung lymphatic vessels showed a small luminal surface and a low density of endothelial nuclei. Pulmonary lymphatic capillaries often formed star-like anastomoses. The structural features of pulmonary lymphatics, including their three-dimensional organization, were distinctly separate from those of the blood microvasculature of the lung.