FUNCTIONAL MICROANATOMY OF INITIAL LYMPHATICS WITH SPECIAL CONSIDERATION OF THE EXTRACELLULAR MATRIX

Abstract

In current conceptions on the functional morphology of initial lymphatics, the extracellularmatrix (ECM) as an integral part of the lymphatic vascular wall has not been duly considered. Inthe present study based on scanning electron microscopy (SEM) and confocal laser scanningmicroscopy (CLSM) of tongue tissue in rats, new insights were obtained into both thearchitecture of the fibrous network of the ECM and its functional features. A digestion techniquewas applied, by which the endothelium of initial lymphatics was detached thereby allowing adirect view of the ECM from both sides. Fluorescent latex particles and liposomes were used asindicators of transmural permeability, whereas labeled macrophages served as a model forpenetrating cells. The two layers of the lymph vascular wall were also examined underexperimental edema conditions with tissue pressures ranging from 10 to 150 mmHg. A concept isproposed which considers the histomechanics of the initial lymphatics with the surroundingconnective fiber tissue including the structural basis for the permeability of the lymphaticvascular wall. The role of the ECM as a supporting element and prefilter for the lymphaticendothelium is emphasized.