Prenatal Development of the Nasal Conchae (Conchae nasales) in Rabbits (Oryctolagus cuniculus)

Nasal conchae increase the sur- face area of these cavities, thus providing for rapid warming and humidification of air and by regulating nasal airflow, play a role in immune surveillance because they are the first intranasal structures to come into contact with outside air. The present study aimed to depict the onset time of the first appearance and origin as well as developmental changes of Nasal conchae.
This study was carried out on 116 rabbit embryos and fetuses of both sexes. all specimens of the heads assembled for normal histological technique, stained with H&E. Some were processed for scanning E/M.
At day13: The primitive nasal cavity was surrounded by a condensation of mesenchymal tissue giving rise the miniature of the nasal


capsule (Fig.8). As well, the anlage of the ventral nasal concha was detected in the lateral nasal wall. At day14: The secondary nasal septum appeared as a wedge like structure formed of mesenchymal connective tissue. It was covered ventrally by a thin layer of undiffer- entiated epithelium which faced the dorsum of the tongue through the primitive choana. At D16: the nasal cavity and the dorsal and ventral conchae plugged inside the nasal cavity and separated by the middle meatus and surrounded externally by nasal capsule. The caudodorsal part of the future nasal cavity demonstrated many folds forming the future ethomoidal conchae. At Day 18: there were many pro- cesses which were differentiated into ectoturbinates and endoturbinates in the ethmoidal region. At Day 20: At the ethmoidal region of nasal cavity showed nerve bundles extended from the covering epithe- lium toward the olfactory bulb. At Day 22: The core of fold contained the cartilaginous extension of ventral nasal conchae was clear. The cells of the olfactory mucous mem- brane were differentiated and the shape of the nuclei of its cells was tapered in the basal cell layer or rounded or oval in the intermediate layers. At Day 25: The ethmoidal conchae had primary and secondary branches housing in between ethmoidal meatuses. The top of the ethmoidal conchae was capped by olfactory epithelium