小鼠肺泡发育与肺泡上皮细胞分化的电镜观察

目的　观察小鼠胚胎及生后肺泡发育及肺泡上皮分化。方法　小鼠胚胎 14天至生后 14天肺组织 ,隔天取材 ,HE染色光镜观察及透射电镜观察。结果　胚胎 14～ 18天 ,小鼠肺的发育以支气管树分支和管壁结构的逐渐完善为主 ,终蕾上皮为柱状或立方状的未分化细胞。胚胎 19天 ,支气管远端形成许多内壁光滑的原始肺泡 ,其上皮分化出Ⅱ型肺泡细胞。生后 1～ 4天 ,肺泡上皮出现少量扁平的Ⅰ型肺泡细胞 ,但仍以Ⅱ型肺泡细胞为主。生后 5～ 14天 ,成熟肺泡形成 ,肺泡上皮以Ⅰ型肺泡细胞为主。结论　出生时 ,小鼠的肺发育只完成了其大体形态的发生 ,肺泡上皮以Ⅱ型肺泡细胞为主。成熟肺泡的形成、数量的增加及Ⅰ型肺泡细胞的大量出现持续到出生后。

Electron microscopic observations of alveoli development and alveolar epithelium differentiation of mouse lung

Objective To investigate the development of the alveoli and the differentiation of the alveolar epithelium.Method Mouse lungs were obtained from E14 the P14,the ultrastructure changes of alveolar epithelial cells were studied by electron microscope.Result At day 14 of gestation(the psudogranular stage),the lung showed a tubular structure,the epithelial cells were columnar cells that have mitochondria,rough endoplasmic reticulum,Golgi apparatus and diffuse glycogen.There are junctional complexes with the epithelial ling cell.At day 16 to 18 of gestation,the glycogen was seen in abundance within the epithelial cells.On the 19th day of gestation,the glycogen content was reduced and a few lamellar bodies were seen in the cuboidal lining cells that would characterized them as type Ⅱ cells.At this time few flattened epithelial cells were also observed,they appeared intermediate in form between type Ⅱ and type Ⅰ cell.These intermediate cells contained glycogen and microvilli and were attenuated as they stretched over the capillaries.From the 1st day to the 4th day after birth,most of the epithelial cells were type Ⅱ cells.The amount of lamellar bodies and mitochondria appeared to be increased.The type Ⅰ cells were first observed at this time.Up to the 7 th day after birth.the alveolar epithelium was mainly composed by type Ⅰ cells.Conclusion Before day 19 of gestation,the changes on fetal lungs were structure devlopment.The type Ⅱ cells were observed at day 19 of gestation,and became the main cells of the alveolar epithelium in the late stage of gestation and a few days after birth.The type Ⅰ cells became the major cells of alveolar epithelium at postnatal lungs,this observation suggested that the type Ⅱ cell would be the progenitor type of epithelium.