Prenatal development of the hard palate in albino rat

The present study was performed to study the details of prenatal development of the hard palate in albino rat considering its structure and maturation using light microscope.Twenty healthy fetuses of albino rats from different gestational ages (between thirteen and twenty-one day of gestation) were used in the present work.Each male was placed over night with one or two albino rat females. The vaginal smear was done each morning by small cotton on small wooden sticks and the vagina was genitally swabbed. This specimen which was obtained, examined under light microscope after staining by toluidine blue for the presence of sperms. If the sperms have presented, the breeding day was considered day zero. Then we started counting to obtain fetuses on desired days. At time of sacrifice, the animals were anaesthetized by light ether inhalation and then dissected, the abdominal viscera were displaced away and the uterine horns were identified and opened. Then the fetuses were delivered from the uterus and immediately placed in acetic acid-formalin-alcohol fixative. The fetuses were subdivided into four groups.The fetuses were subdivided into four groups according to gestational ages:Group A: Included five fetuses aged 13 day of gestation.Group B: Included five fetuses aged 15 day of gestation.Group C: Included five fetuses aged 18 day of gestation.Group D: Included five fetuses aged 21 day of gestation.Head specimens from each fetus were fixed in 10% buffered formaline, then processed and embedded in paraffin wax. Slices of five micron sections were obtained and stained with haematoxline and eosin (H&E) to study the general structure of the hard palate, alcian blue-van gieson method to identify the palatal matrix and connective tissue and verhoeff’s iron hematoxlyin stain to identify macrophages and elastic fiber.Morphological study was done to detect the direction of the palatal shelves, palatal matrix, type of covering epithelium and appearance of osteogenic centre and progression of bone formation.The results of 13th GD revealed that:The earliest sign of secondary palate initiation is manifested as bilateral outgrowths, which emerge from the inner part of the maxillary processes, this sign is not manifested in half of fetuses. The palatal shelves covered by several layers of non differentiated epithelial cells in all directions. The palatal mesenchyma is formed of condensed cells and scanty extracellular mucopolysaccharide matrix..