The Morphology Of The Goat Fetal Lung Development

Morphological Study on Lung of Prenatal Goat Postgraduate : ZHENG Yue-mao Advisor : Prof.ZHANG Yong (College of Animal Science and Veterinary Medicine,Northwest Sci-Tech University of Agriculture and Forestry, Yang Ling, Shaanxi 712100) Abstract Lungs of prenatal goat (4-22 wks) were observed with bare eyes and the lung tissures were observed with LM and transmission electron micro- scopy which showed: 1. The goat fetal lungs have the similar outer appearance in different gestational ages.The left lungs have two lobes and most of the right lungs have four lobes .Most fissures of the fetal lung are incomplete which are connected with lobes by lung tissures and/or serosa tissures All of the lobes of the left and right lungs developed simultaneously. 2. The development of prenatal lungs in goat is divided into five stages: Embryologic stage(3-5wks) The lung bud branching and forming into the two principal bronchi, the principal bronchi increase in length and budding into lobar bronchi ,all the bronchi are lined with stratified columnar epithelium Pseudoglandular stage(6-l2wks): The bronchial divisions differentiated and their air conducting system became established. The terminal bud assumes a glandular aspect.The bronchioles and terminal bud epithelium were differentiated from seudostratified columnar epithelium into single-walled columnar epithelium. The nuclei of the terminal bud columnar epithelial cell transfer to the top of the cells gradually. Short and small microvilli appeared on the luminal surface of the epithelial cells. Mitochondria, rough endoplasmic reticulum and ribosome are all in the top ofthe cells and increased in number with the development of the lungs $ Canalicular stage(13-l4wks):The respiratory bronchioles developed quickly the terminal buds?glandular structures disappeared gradually the respiratory bronchioles and primitive alveoli epithelium were differentiated from single-walled columnar epithelium into cuboid epithelium.The primitive alveoli had developed , the respiratory bronchioles and the primitive alveoli are lined with undifferentiated cuboid epithelium. More short and small microvilli appeared on the luminal surface of the epithelial cells. Mitochondria, rough endoplasmic reticulum and ribosome developed dramatically in the cells.The capillary system developed quickly and approached to the terminal buds gradually. Saccular stage (l5wk): The respiratory divisions developed dramatically and assumed 揳erated?appearance, i.e., the prospective air space volume increases relative to the tissue components. Parts of the primitive alveoli epithelium differentiated into flattened type I alveolar cells and cuboid type II alveolar cells.The osmiophilic bodies were first observed in type II alveolar cells. Alveolar stage (16-22wks): More primitive alveolar epithelial cells developed and differentiated into flattened type I alveolar cells and cuboid type II alveolar cells. The capillary endothelium were pressed close to some of the alveolar epithelium.The alveolar epithelial cells can be d...