In the 10th week of gestation the development of duodenal glands in the bovine intestinum starts by circumscript epithelial proliferation. Their secretory channels are in contact with the crypts. Already in the early fetal stage ultrastructurally there are an inconspicuous equipment with organelles in the apical cytoplasm and single globular granules, which demonstrate the differentiation of epithelial cells into duodenal glandular cells. Until the mid-point of the pregnancy the granular endoplasmic reticulum strongly develops as a condition for the impressive increase in the formation of the prosecretory granules. Finally, in the second half of the pregnancy, granules varying in structure and electronic density, but mostly showing an intensively osmiophilic and fine granular material, are the predominant cytoplasmic structures. Like in goblet cells capsulated vacuoles seem to play a role in the formation of the secretory granules. Recent, extensive studies concerning our results have been discussed.
