A morphometric study of age changes in the histology of the ducts of human submandibular salivary glands

Abstract

Eighty two submandibular glands, evenly representative of sex and eight decades of adult age, were examined histologically for age changes in the ducts. Stratified random point sampling was used to establish the relative proportions of three classes of ducts in individual glands and mean values were calculated for each decade of age. The striated ducts usually formed the largest proportion of the duct system but this reduced with rising age. As a proportion of total gland volume, however, the striated ducts remained constant at 5 per cent irrespective of age. The separate proportions of the duct system occupied by the non-striated intralobular ducts and by the extralobular ducts both increased with rising age. These two categories, therefore, account for the whole of the previously reported increase in the duct fraction of total gland volume which occurs with rising age. Two-thirds of this increase is due to additional non-striated intralobular ducts, many of which are composed of degenerate atrophic or metaplastic epithelium. These changes may increase the effective permeability of the duct system to water and thus might explain the tendency for higher concentrations of some electrolytes in saliva from elderly subjects. Proportions of different classes of ducts, in different age groups, were free of sex differences, as were their rates of ageing changes.