On the development of the chick embryo colon: a computerized morphometric study

The quantitative aspects of the chick embryo colon organogenesis (proximal and distal tracts) have been studied from the 7th to the 15th day of incubation on histological sections by means of a computerized morphometric system. A semiautomatic digital system (Videoplan 2) was used. The area of total section, of the lumen, of the wall and its components (subserous stratum, muscle layer, lamina propria, epithelium) and the thickness of the epithelium and muscle layer were measured; the mean +/- S.E.M. of the obtained values was calculated. The percentage of shrinkage, due to histological procedures, was calculated for each day. The mean values for each day of incubation were modified on the basis of the shrinkage percentage. The differences between the mean values of the areas of the proximal and distal tract were statistically evaluated. Exponential curves and r coefficient were determined to evaluate the general growing pattern of the mean area of colonic wall components as a function of age. The main results demonstrate that in both tracts the component with the greatest growth was the muscle layer, while there are some differences between the proximal and distal tracts of the colonic anlage in the growing pattern of other wall components. The colonic anlage also shows a different developmental behaviour compared with that of the chick embryo ileum and duodenum.