[Fetal development of the omasum of cattle (Bos taurus)]

Structures characteristic of the omasum are already present by the third month of development. The fetal omasal laminae exhibit their typical arrangement (1434243414). Muscle fibers from the lamina circularis also extend into the first through third order laminae at this stage. Conical projections and small secondary papillae begin to appear on the laminae as the fetus ages. The lamina muscularis mucosae can be found in all of the laminae by the fourth to fifth month of development. The cuboidal to columnar epithelium of the stratum basale remains largely unaltered throughout the course of fetal development, whereas the stratum superficiale is subjected to a continuous series of changes. Superficial cell layers increase and the glycogen content of the epithelial cells fluctuates significantly.