Observations on the histogenesis of bovine ruminal papillae.

Changes in numbers of epithelial and connective tissue cells, thickness of connective tissue, and height and diameter of papillae were quantitated in fetal and postnatal bovine ruminal mucosa. During fetal development, the height of papillae and number of fibroblasts increased, the diameter of papillary base and thickness of subpapillary and interpapillary connective tissue remained constant, and the numbers of basal and superficial cells of the epithelium decreased. During the first 2 months of postnatal development, the height of papillae and numbers of fibroblasts enclosed in the papillary core decreased, and the diameter of the papillary base and the interpapillary distance increased. In consequence, the increase in connective tissue, rather than its redistribution, was involved in papillary development. The epithelial reorganization appeared to follow the changes occurring in the connective tissue, at least during fetal development.