Morphometric studies on the development and sexual dimorphism of the submandibular gland of the mouse.

A light microscopic morphometric analysis of the development of the mouse submandibular gland has been carried out from birth up to the age of 6 weeks. At birth the bulk of the gland consists of approximately equal volume proportions of acinar, terminal tubule and non-secretory cells. The granular convoluted tubule is absent at birth. The neonatal female gland resembles that of the male in many respects. With the regression of the terminal tubule at 2 weeks of age the duct system of the gland is seen to differentiate into excretory, striated and intercalated ducts. The volume proportions of the gland constituents of the female are similar to those of the male at 2 weeks. At this age, the acini occupy 55%, the striated duct 20% and the intercalated duct 15% of the total gland volume. Sexual dimorphism is clearly evident in the gland at 4 weeks of age when the duct system is seen to differentiate to form its granular convoluted tubule component. The granular tubule occupied 19% of the gland volume in the male but only 8% in the female at 4 weeks. The proportions of acini are only 41% in the total gland volume of the male mouse but 62% in the female at 4 weeks. In the male gland the proportions of granular convoluted tubule increase from 13% to 21% between 4 and 6 weeks and the secretory granule content of these cells from 6% to 24%. At 6 weeks of age the volume proportion of granular convoluted tubule in the male is 45% and that in the female is only 12%. At this age the acini occupy a proportion of 30% in the male gland as opposed to 57% in the female gland. At 6 weeks the volume of granular convoluted tubule cells is 40% lower in the female (1842 microns 3) than in the male gland (2995 microns 3).