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.The lymphatic system of vertebrates is responsible for the reabsorption of part of the water and electrolytes and most of the proteins that are continuously leaving the minute blood vessels to bathe the cells of the body tissues [Drinker, 1946;Courtice and Morris, 1955]. The importance of this function can be appreciated in the rapid deterioration in the condition of animals and human beings with chronic thoracic duct fistulae which are draining large quantities of lymph to the exterior Drinker, 1946]. Lymphatics of the tissues, in order to fulfil their physiological role, must have two important properties. One is to be able to collect fluid from the tissues, and the other is to move the fluid away from the site of collection and back, generally via the thoracic duct, into the circulating blood stream. Valuable information has been obtained from in vivo observations of lymphatic function in the amphibian tail [Clark, 1912;Clark and Clark, 1920], in the rabbit ear chamber [Clark and Clark, 1932, 1933, 1937, in rat mesentery [Webb, 1933], in the mouse ear [McMaster, 1947;Pullinger and Florey, 1935], in a variety of acute dissected preparations in mammals [Florey, 1927;Pullinger and Florey, 1935;Smith, 1949] and in the membrane of the bat's wing [Webb and Nicoll, 1944]. There has not been any direct extension of in vivo observations such as these so as to correlate observed physiological function with ultrastructural morphology on the identical vessel. The present experiments were performed to relate the in vivo properties of selected lymphatic vessels in the wing membrane of the bat with their ultrastructure observed after fixation and embedding for electron microscopy.

The morphology of valves and valve-like structures in the canine and feline thoracic duct

“…In this study we have observed some aspects of the microanatomy and ultrastructure of the ThD and its march valves that have been previously reported (Albertine et al 1982;B6rst et al 1969;Casley-Smith 1969;Cliff andNicoll 1970, Daroczy 1984;Gnepp 1976;Gnepp andGreen 1979, 1980;Lauweryns and Boussauw 1973;Marais and Fossum 1988;Schipp 1968;Takada 1971;Vajda and Tomcsik 1971). Our own observations have allowed us to systematize and review the previous data in the light of modern liquidodynamics in vessels and the functions of the cytoskeleton.…”

The Effect of Vasoactive Agents on the Contractions of the Initial Lymphatics of the Bat’s Wing

“…Part of the explanation for the difference in response may be in the innerva tion of the mesenteric lymphatics [Vajda, 1966;Alessandrini et al, 1981;Ohhashi et al, 1982] and the apparent absence of inner vation of the lymphatics in the bat's wing [Fleming and McKinney, 1985], The con tractile elements of the mesenteric lymphat ics may also be different from the initial lym phatics. Initial lymphatics of the wing of Miniopterus schreibersi, an Australian bat, consist of only a single layer of endothelial cells [Cliff and Nicoll, 1970]. Nicoll [1975] believed that typical vascular cells were also lacking in the spontaneously contractile ini tial lymphatics of the wing of the little brown bat, Myotis lucifugus.…”

Venomotion modulates lymphatic pumping in the bat wing

“…The possibility that venular and lymphatic contractions are both initiated by a common neural, electrical, or humoral factor must be addressed. First, venules and lymphatic microvessels in bats are not innervated (6,28,54). If a venule and an adjacent lymphatic microvessel were jointly innervated in the bat wing, there would have to be a consistent delay before the initiation of lymphatic contraction.…”