Topography and ultrastructure of the uterine lymphatics in the rat.

An integrated light and electron microscopic study of the rat uterine lymphatic microcirculation reveals that the functional layer of the endometrium lacks an intrinsic lymphatic system. Only some scanty lymphatic capillaries may be observed in the basal endometrium near the endo-myometrial junction; these are in fact initial lymphatic capillaries belonging to the well-developed plexus of myometrial lymphatic capillaries which rarely permeate the entire myometrial internal muscle layer, ending blindly in the basal endometrium. The ultrastructure of these initial 'endometrial' lymphatic capillaries is detailed. The myometrium, in contrast, has a rich supply of lymphatic capillaries as well as lymphatic vessels, the latter provided with many valves. Both the topography and the fine structure of myometrial lymphatic capillaries and lymph collecting vessels-including their valves-are described and discussed.