Histogenesis Of The Mongolia Sheep Embryonic Lung

We have studied the histogenesis and histology changes of the lung tissue of embryo of Mongolia sheep during the different stage of the length of embryo. At the stage of 4mm length embryo of Mongolia sheep,laryngotracheal groove,which is longitudinal slit-like apertura that form laryngotracheal,was detected on the basal layer of pharynx. At the stage of 10mm length embryo ,tracheary bud have formed two tubuloacinar ramification which develope and form left and right major bronchi. Before the stage of 85mm length embryo,the stage is pseudoglandular period of embryo development,and the whole lung tissue were composed of tracheary bud which is concentrated and have tiny calamus. Begin with the stage of 85mm length embryo,in the lung tissue, a lot of big bronchi were found whose externa have obvious cartilagines,and tunica submucosa mixed glands were found.And at this time,the lung tissue of embryo begin to enter canalicular period. From the stage of 250mm length to 347mm length embryo ,the development stage of fetal lung is called terminal sac period or primitive alveolar period. In this period, primitive alveolar differentiated while capillary blood vessel reduplicated quickly. From the stage of 400mm (130days) length embryo to prenatal embryo,the structure of lung have evident difference with terminal sac period,and it is similar with adult.This stage is called prenatal period. In the lung tissue of 300mm length embryto,type â… -like and â…¡-like alveolar was detected by electron microscope. type â… -like alveolar is spindle-shaped, and it's nucleus is irregular,and nucleolus isn't obvious,and it's cytoplasm is rare. Having rich cytoplasm,evident nucleolus,much organelle and mitochondrion, rich rough endoplasmic reticulum,and not having secretory granule, type â…¡-like alveolar is cubic. After the stage of 400mm length embryo,typical type â…  and type â…¡ alveolar have formed in the lung tissue. Many type â…¡ alveolar have typical incretory particle.