Morphogenesis of the intestinal villi of the mouse embryo: chance and spatial necessity
Sbarbati, R.
Journal of Anatomy 135(Pt 3): 477-499
1982
ISSN/ISBN: 0021-8782 PMID: 7153168 Document Number: 186551
The duodenum and colon are adjacent organs with a different morphogenesis but they show a common developmental pattern, the formation of villi. To determine if the morphogenesis of the villi in both organs is brought about by dynamic interaction between epithelium and mesenchyme, in particular by differential changes in their growth rates within the geometric framework constituted by their interrelated spatial position, mouse embryos of the CPB-S strain aged between 12 and 16 days after fertilization were used. They were sectioned at constant thickness (10 and 1 .mu.m). Cross sections of the duodenum and large intestine were selected as originating from corresponding straight parts of the intestinal tube at different ages. The following parameters were estimated by means of a morphometric method: cross-sectional area of the epithelium and of the mesenchyme, outer circumference of the intestinal tube and length of the borderline between the epithelium and the lumen. Epithelium and mesenchyme of the duodenum grow differently from epithelium and mesenchyme of the colon, e.g., they present different cross-sectional areas and specific growth rates. In both cases mesenchyme grows more slowly than epithelium and the ratios between the specific growth rates of the layers (e.g., the allometric curves) are similar throughout growth. Apparently, the dynamic interaction of the layers produces qualitatively similar shapes. The mutual interaction of epithelium and mesenchyme produces at any time enlargement of the surface between epithelium and lumen, and constancy of the ratio epithelial mass/epithelial surface. A boundary condition for the process is the preservation of the lumen. Apparently, chance plays a role during morphogenesis. Random generation of cells in time and/or space might be involved in the origin of biological structures such as villi.