Fenestrated endothelia in vessels of the nasal mucosa. An electron-microscopic study in the rabbit.

The ultrastructure of the vessels in the normal respiratory and olfactory mucosa of the nasal septum was studied in 15 adult rabbits. Capillaries with continuous and fenestrated endothelia could be observed in both tissues. In the respiratory part, many of the fenestrated capillaries were located subepithelially with their fenestrations facing the adjacent epithelium. Fenestrated capillaries of the olfactory mucosa were found mainly in the deeper parts of the tunica propria and usually revealed only a small number of fenestrations in their endothelial lining. It was also demonstrated that muscularized veins sometimes displayed fenestrated areas in their attenuated endothelia. These results are discussed and compared with the appropriate literature. Our results confirm that there is a link between the morphological peculiarities of the vascular wall and the functional behaviour of the nasal mucosa. These findings also emphasize that endothelial fenestrations seem to be characteristic for a certain segment of the microcirculatory system rather than for a distinct type of capillary vessel.