Fine structure of the epithelia of the vomeronasal organ of horse and cattle. A comparative study.

The vomeronasal organ of both horses and cattle is a tubular structure situated bilaterally at the base of the nasal septum. In frontal plane the shape of its lumen is semilunar to crescent. The sensory epithelium lining the medial wall of the lumen contains receptor, supporting and basal cells with some surface modifications in both species. In the horse, a structure similar to a microprocess was observed among the microvilli of receptor cells. In cattle, a large mass of the cytoplasm of the receptor cell occasionally protrudes to form a bleb-like structure. The supranuclear cytoplasm of the receptor cells contain mitochondria, free ribosomes, rough endoplasmic reticula, Golgi apparatus, lysosomes and multivesicular bodies. Some receptor cells were pyknotic. In both species the respiratory epithelia of the lateral wall of the lumen contain ciliated, non-ciliated and basal cells. In the horse, this epithelium differs from that of other species in evidence of prominent secretory function.