TEM micrographs of alligator nasal epithelia. A OSN (type I) with few mitochondria. The long arrow points to a centriole deep in the cytoplasm of the OSN. Short arrow – basal body of cilia. sc – supporting cell. B Basal portion of the olfactory epithelium. The basal lamina (arrowheads) follows the undulating shape of a basal cell (bc). Axons (ax) aggregate above the basal lamina into fila olfactoria that will penetrate the basal lamina in a different location. C Solitary chemosensory cell (SCC) in the olfactory epithelium. The cytoplasm is filled with small vesicles. The surrounding supporting cells (sc) constrict the apical ending of the SCC into a "neck" (small arrows). Large arrow – OSN. D Nonsensory epithelium in the most ventral part of the nasal cavity. Among ciliated nonsensory cells (arrowheads), a cell with small microvilli-like protrusions contains vesicles of various sizes (compare Fig. 5E). Debris-containing vesicles (arrow) suggest a phagocytotic function. E Another type of nonsensory epithelium with cells that bear no cilia but only small microvilli-like protrusions. The cytoplasm is also filled with vesicles of various sizes as seen in D, but cell debris never occurred within these cells. n – nucleus; vs – vesicles.