Variation and density of microplications in superficial cells of the normal oral lining mucosa in the monkey Macacus fascicularis

Abstract

A scanning electron microscopic study on the oral surfaces of the buccal and labial mucosa of Macaca fascicularis was carried out to determine the variation and density of the microplication patterns expressed by the outer surface of superficial cells of non-keratinizing oral epithelium. Micrographs were recorded at two levels of magnification. A total of 76 micrograph pairs were used to estimate stereologically the visible cell surface area, the total microplication length and density per cell, as well as the frequency of occurrence of eight particular plication features. The visible surface area of cheek cells was slightly but insignificantly smaller than that of labial cells, with a proportional difference in the total microplication length. The basic microplical surface features were identical in cheek and lip cells but some, such as bifurcations and most types of free endings, occurred more frequently in lip than in cheek cells. The plication density ranged from 120 to 550 μm/100 μm 2 cell surface area. Independent of microplication density but based on the type of feature combination, four different microplication patterns could be distinguished, which occurred with equal frequency in both cheek and lip cells. The functional meaning of cell surface microplication is discussed in terms of several hypotheses: (1) intercellular interdigitation for the purpose of adhesion, (2) protection by way of reducing the surface area of cell contact, (3) channel formation for aiding laminar flow distribution of lubricating secretions, and (4) reserve surface area for cell stretching.