Lymphatic vessels in the oral cavity: different structures for the same function.

A study using a light and transmission electron microscope was performed on some structural characteristics of the lymphatic capillaries in different regions of the human oral cavity. The lymphatic capillaries of dental pulp, masticatory mucosa (gingiva and peri-implant mucosa) and lining mucosa (cheek) were examined. Our attention was focused on the morphologic characteristics of the endothelial wall in the lymphatic capillaries. In particular, the connections between endothelial cells were investigated. In the lymphatic capillaries of the dental pulp, the endothelial wall was always very complex. It frequently presented protrusions of the endothelial cells that overlapped and formed intercellular channels. These channels were thus contained by the vessel endothelial wall with their extremities opening out towards the surrounding interstitium and the vessel lumen. The endothelial wall of the lymphatic capillaries of the cheek was very smooth and thin without complex intercellular junctions. The endothelial cells were joined by end-to-end junctions and open junctions were frequently observed. Intercellular channels were also found in the endothelial wall of lymphatic capillaries of the gingiva and the peri-implant mucosa. The presence of numerous clefts represented by the open junctions in the lymphatics of the cheek and the existence of complex intercellular adhesions with the formation of intercellular channels in the endothelial wall of the lymphatic capillaries of the dental pulp and gingiva induce us to believe that these may play a role in the various mechanisms used by lymphatic capillaries to absorb interstitial fluids. These mechanisms are based on the different morpho-functional characteristics of the surrounding tissue. (C) 2002 Wiley-Liss, Inc.