Microvascular architecture of the hard palatine mucosa in the rabbit.

SEM studies on the microvascular architecture of the hard palatine mucosa, especially the transverse palatine plicae, and the morphological relations between the microvasculature and layers of the hard palate mucosa of the rabbit, were carried out by the acryl plastic injection method. The findings were compared with those obtained previously in the cat and Japanese monkey. Morphological differences and similarities between the papillae in the lamina propria and the capillary loops in the papillae were elucidated by SEM. A boneless area was found in the hard palate since the palatine fissures occupied a large area between the diastemata. The transverse palatine plicae numbered 14-16 symmetrically in the hard palate, and were more developed than those in the cat and Japanese monkey. In sagittal sections of the hard palate, the transverse palatine plicae were observed to be serrated, since they were located close to each other with small narrow interplical regions. The plical branches were usually derived from the major and minor hard palatine arteries, and formed the primary arterial network in the submucous layer of the hard palate. Twigs diverging from this network formed the second arterial plexus in the lamina propria, and furthermore, a subepithelial capillary network was formed immediately beneath the epithelium. From this network, capillary loops sprouted into papillae. Similarities were found between the papillae and capillary loops with locational differences. The descending crus of the capillary loop drained into the venous site of the subepithelial capillary network which flowed into the primary venous plexus in the lamina propria, which finally poured into the second venous plexus in the submucous layer. This plexus was termed the palatine venous plexus, and was especially well-developed in the area covering the palatine fissures. The capillary loops in the plica displayed characteristic features according to the portions within it and the interplical regions.