The vomeronasal system of the mink, Mustela vison. I. The vomeronasal organ.

The vomeronasal organ (VNO) of the mink is restricted to the area of the Fissura palatina and thus always topographically related to the Ductus incisivus (DI). The VNO and DI have also a functional relation because the vomeronasal duct ends in the incisive duct. On the other hand, as the DI has its mouth in the Papilla incisiva there is a communication between the VNO and the oral cavity. The vomeronasal cartilage, approximately in 1/6 of its length, wraps completely the parenchyma of the VNO whose main structure is the vomeronasal duct, with two different epithelia: sensory receptor in the medial wall, and respiratory in the lateral one. Nevertheless the variations of epithelia belong to the segment of the duct because in its rostral and caudal parts the medial and lateral epithelia are very similar. Branches and tubular PAS positive glands stand out in three points: superior, inferior and medial areas of the vomeronasal duct in which they end. An important number of vessels, mainly veins of different diameter, are located around the duct, while the nervous fibers are close to the medial wall of the duct and very easy to identify in the caudal third of the organ. Two immunohistochemical techniques were used to identify the nerve fibers and the receptor cells.