The soft-tissue components of the vomeronasal organ in pigs, cows and horses.

The soft-tissue components of the vomeronasal organ of the pig, the cow and the horse were studied with the aid of dissection, microdissection, and light microscopy and immunohistochemistry of series of transverse sections. In horses, the rostral end of the incisive duct was blind: thus, unlike in pigs and cows, there was no communication between the vomeronasal organ and the oral cavity. In all three species, the central part of the vomeronasal duct bore the 'typical' respiratory/ receptor epithelium lining on its lateral and medical walls. The rostral part of the duct was characterized by stratified columnar epithelium, while more caudal parts bore simple columnar type. The patterns of distribution of glands, blood vessels and nerves were closely associated with the patterns of distribution of duct linings. The distribution of soft-tissue components in pigs was less clearly defined than in cows and horses. Of the three species, nerves were detected in the rostral half of the vomeronasal parenchyma only in the horse.