Differentiation of the Olfactory Epithelium in Sheep in Ontogenesis Using Scanning Electron Microscopy

Tic h Y F., D. H 0 r k y, I. M i ~ e k: Differentiation of the Olfactory Epithelium in Sheep in Ontogenesis using Scanning Electron Microscopy. Acta vet. Bmo 1995, 64:71-77. The method of scanning electron microscopy was used to study the differentiation of the olfactory epithelium and the formation of the surface of the olfactory epithelium of sheep on the 74th and 79th days of prenatal period, on the day of birth, 30 days after birth and in an adult animal of 730 days of age. From the 74th day of Lu. development, the olfactory endings on the surface of the olfactory epithelium were found to be on different levels of development. Their amount gradually increased prior to birth as did the amount of olfactory cilia growing out of these olfactory endings. The cilia were formed fIrst, in the range of proximal segments; distal segments of cilia appeared later, in dependence on the degree of differentiation of the olfactory endings. No microvilli were yet formed on the apical segments of the sustentacular cells of a 74-day old foetus. They began to differentiate after the 79th day of Lu. development and most of them were not formed until the immediate perinatal period. In the postnatal period the amount of newly formed olfactory endings decreased, but the number and length of olfactory cilia continued to increase. Areas of regenerating olfactory epithelium and individual differentiating olfactory endings could also be observed in an adult animal. Differentiation, microvilli, olfactory epithelium, olfactory cilia, sheep Many authors studied the structure and ultrastructure of the olfactory epithelium using light microscopy as well as transmission and scanning electron microscopy. In literature we can find detailed data about the structure of this epithelium in fish and amphibians (FarbmanandGesteland 1974; U sukuraandYamada 1978;Franceschiniand Cia n i 1991), in birds (G r a z i a d e i and Ban n i s t e r 1967; B rei p 0 h I and Fer nan d e z 1977) and particularly in various mammals (B rei p 0 h 11972; And r e w s 1975; Yamamoto 1976;MencoetaI. 1976, 1978;Menco 1977, 1988;Mendozaet aI. 1992; and others) and man (B u s u t til et al. 1977; M 0 ran et al. 1982; and others). In numerous communications the epithelium was compared in various mammals or vertebrates (G r a z i a d e i 1971a, 1973ab, 1974, 1975; B rei p 0 h 1 et aI. 1974ab; K e r j as c h k i 1978; Get c h e 111986; and others). The basic classification of cells of the olfactory epithelium is similar in ail the hitherto studied animal species. Most of the morphological studies involve descriptions of the olfactory receptors proper and of the sustentacular cells (M 0 u 1 ton and B e i die r 1967; G r a z i a d e i 1973a; Men co 1977; and others), particularly the distribution of olfactory endings and the structure of the deflecting olfactory cilia (S e i fer t 1970; Men c 0 et aI. 1976; Men co 1977, 1988). The olfactory cilia, namely their distal segments are considered to be the bearers of receptor loci (Kerj as chki andHorandner 1976; GetcheII1986). In literature considerable attention was devoted to the description of apical segments of sustentacular cells (S e i fer t 1970; Men co 1977) particularly to the structure and function of their microvilli (K e r j a s c h k i and H 0 ran d n e r 1976; Men c 0 et al. 1978). The function of the sustentacular cells is usually compared with the function of gliocells (B rei p 0 h 1 et al. 1974b). Some authors (M 0 u 1 ton and