Morphogenesis and computed tomographic study on maxillary and ethmoidal conchae as well as their related nasal sinuses in New Zealand White rabbits: prenatal and postnatal development
Authors: Haddad seham said , Rashed Reda , Areisha Atef mohamed 
Published: December 2023

Background:
The development of maxillary and ethmoidal conchae in New Zealand white rabbits is one of nasal cavity components which is derived from three embryonic sources: ectoderm, neural crest, and mesoderm. The ectoderm forms nasal placodes, while the neural crest provides facial mesenchymal tissue. Frontonasal processes give rise to medial and lateral nasal processes, forming the nasal capsule from which the maxillary and ethmoidal conchae are arise.
The distinctive symmetry and branching of New Zealand white rabbit (NZW) maxillary nasal or ventral conchae and ethmoidal nasal conchae and their related sinuses, make an invaluable model for research and laboratory use. In this study, forty nasal cavities of NZW rabbit embryos and fetuses in the prenatal, neonatal, and postnatal stages are examined. grossly by using stereomicroscope, classic serial histology section by specific stain (H&E, Trichrome, and Toluidine blue stain) and computed tomography (CT) imaging technique. The first observation of primordial ventral nasal conchae called maxillary conchae which are present in the middle of the nasal champers occurred at E19 days of pregnancy from the lateral nasal capsule, emerge as epithelium, fragile elevations that are subsequently strengthened by chondral plates at E21 of prenatal life., then grow and take form as mushroom like shape within middle nasal cavity at E23, then ramify into three finger-like spiral branches ( secondary branching lamellae) on day E25& E28 of pregnancy till increased in their branching and ramification at one month of postnatal age till occupy the most of NZW rabbit nasal cavity resembling the arborization like tree; and separated and guarded by common nasal meatus from septum nasai and meatus middle nasalis from nasal concha dorsalis and from the floor of cavity nasalis by ventral nasal meatus and covered by respiratory epithelium(pseudo stratified columnal ciliated epithelium with goblet cells). Their ossification is taking place firstly at the basal plate of the ventral nasal conchae after birth; the ventral spiral lamellae were completely ossified at week old postnatally.
At the lateral aspect of newly formed maxillary conchae; there are maxillary sinuses appear as small one champers in one side of recently developed cavum nasi laterally at E23 &E25 birth then increased in its width to form two compartments and recesses on both side of cavum nasi connected by nasolacrimal duct at one month of postnatal age.
Concerning the ethmoidal nasal concha, it was first seen as a little bud occupy the caudal half of nasal cavity and appear at E28- day age of gestation &E0 (birth day) covered by olfactory epithelium; and ends its branches postnatally into four ecto- and four endo-turbinate. at one week old after birth and become well convoluted and more curling within the nasal fundus at two weeks and one month age of postnatal life.
The ethmoidal sinus appeared as air filled spaces in between the ethmoidal conchae and labyrinths; it doesn't excavation or pneumatization of the ethmoidal conchae as the dorsal conchal sinuses but they appeared as open spaces in between the ethmo-turbinals located at the caudal half of the nasal cavity; it appears only at the postnatal age of two weeks old of NZW rabbit,
The aim of current investigation is required to illustrate the timing of the initial appearance, the place of origin, and the changes in maxillary and ethmoidal conchae development and their related nasal sinuses in New Zealand rabbit (NZW).