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

In current conceptions on the functional morphology of initial lymphat ics, the extracellular matrix (ECM) as art integral part of the lympha tic vascular wall has not been duly considered. In the present study b ased on scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM) of tongue tissue in rats, new insights were obtaine d into both the architecture of the fibrous network of the ECM and its functional features. A digestion technique was applied, by which the endothelium of initial lymphatics was detached thereby allowing a dire ct view of the ECM from both sides. Fluorescent latex particles and li posomes were used as indicators of transmural permeability, whereas la beled macrophages served as a model for penetrating cells. The two lay ers of the lymph vascular wall were also examined under experimental e dema conditions with tissue pressures ranging from 10 to 150 mmHg. A c oncept is proposed which considers the histomechanics of the initial l ymphatics with the surrounding connective fiber tissue including the s tructural basis for the permeability of the lymphatic vascular wall. T he role of the (ECM) as a supporting element and prefilter for the lym phatic endothelium is emphasized.