STRUCTURE AND FUNCTION OF LYMPHATIC VESSELS OF THE BAT'S WING

Abstract

The lymphatics of the bat's wing could be separated in vivo into two morphologically and functionally distinct types. Vessels selected for subsequent electron microscopy were labelled in vivo with Berlin blue which could be readily identified in the electron microscope. The terminal bulbs which are responsible for absorption of fluid and particles from the tissues have walls composed of a single layer of endothelium lined on its abluminal surface by a generally tenuous condensation of fibrillar material. Absorption is considered to occur through large gaps present in the endothelial lining. Although the endothelial junctions have no specialized attachment zones, no evidence was obtained for any flap‐valve action in these regions. No gaps were found in the endothelial layers of the collecting and transport channels. The transport channels which are contractile and are responsible for the propulsion of lymph in vivo contain smooth muscle cells in their walls. These cells are not innervated. The cusps of the lymphatic valves are simply two layers of endothelium separated by a narrow zone containing fine fibrillar material. The endothelial cells are phagocytic to the marker particles. © 1970 The Physiological Society