Ultrastructure of the venous ampulla in the interradicular microvascular bed of the mandibular molars of Mus musculus.
The interradicular periodontal ligament of mandibular molars contains an apparently unique dilated vessel straddling the interradicular alveolar bone. This structure is designated a venous ampulla. The vessel possesses a luminal length and width of approximately 200 X 100 microns, respectively. Ultrastructurally, the endothelium has an average thickness of 0.35 micron, a continuous basement membrane, and an incomplete layer of pericytes. Open endothelial junctions are not present. The anatomy of the vessel wall differs markedly on the dental- and bone-related aspects. Calculated ratios for the luminal diameter to wall thickness vary from 1:80 to 1:150. Postcapillary-sized limbs from this vessel drain into the interradicular septum of bone and the ligament microvascular bed. Arterial supply to the ampulla is provided via arteriovenous anastomoses characterized by their association with myelinated and unmyelinated nerve groups. Oxytalan fibers are present throughout the wall of the venous ampulla, penetrating to the abluminal side of the endothelium where they are associated with unmyelinated axons and free nerve endings. Elsewhere, oxytalan fibers are related to the arteriovenous anastomoses and their accompanying myelinated and unmyelinated nerves located adjacent to the endothelium. Pericytes form membranous contacts with the endothelium of the arteriovenous anastomoses and have processes penetrating the endothelium basement membrane.
D000818:Animals; D001485:Basement Membrane / Q000648:ultrastructure; D004727:Endothelium / Q000648:ultrastructure; D008334:Mandible; D051379:Mice; D008815:Mice, Inbred Strains; D008854:Microscopy, Electron; D008963:Molar / Q000098:blood supply* / Q000648:ultrastructure; D014680:Veins / Q000648:ultrastructure*