LYMPHATIC CAPILLARIES OF THE PIG LUNG - TEM AND SEM OBSERVATIONS

Pulmonary lymphatic vessels extend within the connective tissue sheets surrounding airways and blood vessels. Frequently in this location th ey also border the lobular parenchyma, but no lymphatic vessels have b een found within intralobular compartments between blood capillaries a nd alveoli. The presence and distribution of lymphatic vessels in pulm onary tissue are consistent with an important role for the lymphatic s ystem in the clearance of interstitial fluids in the lung. Pulmonary l ymphatic channels have structural characteristics of initial lymphatic s; their walls are formed only by an endothelial layer, and no muscula r cells are present. A network of anchoring filaments and collagen and elastic fibers surrounds the vessel walls. Because the lung is a mobi le organ the tissue undergoes compression and distension during respir atory phases. These modifications could have a role in the mechanisms for lymph formation and flow. (C) 1994 Wiley-Liss, Inc.