INITIAL LYMPHATICS- MORPHOLOGY AND FUNCTION OF THE ENDOTHELIAL CELLS

Abstract

In considering lymph formation, thefunction of the initial lymph sinus is usuallyconsidered a passive process. The cells,however, of the initial lymphatics hold a keyposition in absorbing fluid from the interstitialspace. The present study using rats and guineapigs in different days of the estrus cycle orpregnancy examined by light, scanningelectron, and transmission electron microscopysuggests that the forming and closing of theopen-junction formations is an active componentof the lymphatic endothelium. Openinterfacestructures represent a further entryinto initial lymphatic pathways. The existenceof "endothelial cellular buds" probably actstructurally to build elements of the initiallymph sinus. In short, the endothelium of theinitial lymphatic sinus appears to be astructure of utmost flexibility able to respondpromptly to increased amounts of lymph fluidtransported from the interstitial space.