Three-dimensional organization of lymphatics in the dog small intestine: a scanning electron microscopic study on corrosion casts.

Casts of the lymphatics of the canine small intestine were made by direct injection of a low viscosity methacrylate resin into a large lymphatic in the submucosal layer, and observed under a scanning electron microscope. The lymphatics started with rod-like central lacteals in the villi of the jejunum and leaf-like ones in those of the ileum. The bases of the lacteals were connected by slender lymphatics forming a three-dimensional network, tentatively called the "superficial lamina propria lymphatic plexus". From this plexus, a few straight branches descended through the lamina propria to drain into a well developed "deep lamina propria lymphatic plexus", which was extended two-dimensionally closely above the lamina muscularis mucosae. From this plexus, a few short lymphatics extended and penetrated the muscularis mucosae and drained into the "superficial submucosal lymphatic plexus", a coarse mesh work of thick lymphatics. From this plexus, a few slender lymphatics descended to drain into a second lymphatic plexus, called the "deep submucosal lymphatic plexus", which extended two-dimensionally on the circular muscle layer. This deep submucosal plexus was a coarse network of thick knotty lymphatics. A large collecting lymphatic was occasionally seen running through the mesh. The tunica muscularis contained tubular lymphatics extending horizontally parallel to the muscle fiber, both circular and longitudinal.