The ontogeny of the olfactory epithelium:: An ultrastructural study in sheep

Ultrastructure of the olfactory epithelium was studied in ovine foetuses aged 74 and 79 days, in newborn and 30-day-old lambs, and in a 730-day-old sheep. Differentiation of apical parts of Supporting cells, cilia on sensory cell dendrite endings, redistribution of centrioles from dendrite into endings and presence of a large amount of glycogen inclusions in Supporting cells were apparent at day 74 of the intrauterine development. Supporting cells represented the major portion of the olfactory epithelium at day 79. The epithelial surface was covered by a dense network of cilia. but distal segments were seen only sporadically. The amount of micrombuli increased in dendrite cytoplasm. At birth, the cytoplasm of olfactory endings contained numerous light vesicles, mitochondria and centrioles. The free surface of supportive cells was furrowed into numerous microvilli. Distal segments of olfactory cilia were observed at the age of 30 days only. The segments contained a reduced number of axial microtubuli and contacted microvilli of supporting cells. The pattern and ultrastructure of olfactory cells of an adult sheep did not differ from those of a 30-day-old lamb. Degenerating olfactory cells were observed only sporadically. Supranuclear cytoplasm of supporting cells contained glycogen inclusions and bundles of tonofibrils.