The presence and significance of intraepithelial mesenchymal cells in human foetal colon.

During an investigation of the morphogenesis of the human foetal colon, breaks in the basal lamina underlying the surface epithelium were frequently observed at 10 1/2-11 weeks. These occurred at those sites where the mesenchyme was sweeping up into the epithelium prior to the transformation of the epithelium from stratified to a single layer. At the same time numbers of mesenchymal cells appeared among the epithelial cells and some were observed actually in the process of passing through the gaps in the basal lamina. Close contact was apparent between some mesenchymal cells and basal epithelial cells through extended breaks in the basal lamina. Many of the mesenchymal cells within the epithelium contained numbers of apoptotic bodies. This suggests that one of the functions of the intra-epithelial mesenchymal cells is to remove the debris resulting from cell death which occurs in association with the re-arrangement of cells during development of the colon.