PRENATAL DEVELOPMENT OF THE VOMERONASAL ORGAN IN RABBIT

Abstract

The vomeronasal organ (VNO) is the peripheral receptors, with the ability to detect pheromones, and so it has a role in social behavior, sexual reactions and reproduction. The aim of this study was to designing, categorize, define and demonstrate the normal explaining of the onset time of first appearance and origin as well as developmental changes of vomeronasal organ of the rabbit and its allied structures. This study was carried out on 116 rabbit embryos and fetuses of both sexes. The specimens were obtained, from 14 normal and apparently healthy adult female rabbits. At days (D) 9-11 of pregnancy the nasal placode was invaginated to form the nasal (olfactory) pits. The primordia of the VNO was formed at the ventromedial area of this nasal pit. At D13, the VNO appeared as bilateral un-differentiated epithelial thickenings of the rostroventral part of nasal septum. At D14, the dorsomedial part of the epithelium was about a twice as thick as its ventrolateral part. At D16the VNO opened into the nasal cavity the miniature VNO nerve fascicles were appeared. At D18, VNO immature glands appeared in the dorsolateral part of the VNO the chondral plate was differentiated into chondroblasts. The lumen of the VNO was extremely increased in wide and closed to be oval lumen. At D20, the rostral opening of VNO duct opened directly into the floor of nasal cavity. The medial wall was thicker and had about 8-10 layers of stratified columnar and the lateral one consisted of 3-4 pseudostratified columnar cell layer. At D22, the of acini of the VNO glands determined at the dorsal commissure of the VNO duct. At D28, the lumen was lined by a thick medial mucosa with stratified olfactory like epithelium and thin ventrolateral respiratory epithelium. Key words fetus; vomeronasal organ; nerve; glands; olfactory epithelium; respiratory epithelium