国人胎儿肺泡发育与上皮细胞分化的透射电镜观察

目的 观察国人胎儿肺泡发育及肺泡上皮的分化过程。方法 自愿水囊引产的国人胎儿10~34周肺组织,HE染色光镜及透射电镜观察。结果 胎儿10~16周,胎肺的发育以支气管树分支和管壁结构的逐渐完善为主,终蕾上皮为柱状的未分化细胞。17~24周,支气管树的分支明显增多,上皮细胞的分化趋于成熟。胎儿25周以后,支气管远端形成许多内壁光滑的原始肺泡,其上皮细胞以一种胞核较大,胞质核细胞器较少的原始细胞为主,但开始分化出Ⅱ型肺泡细胞。此时,肺泡上皮亦出现少量扁平的Ⅰ型肺泡细胞,但以Ⅱ型肺泡细胞为主。32周时,肺泡的发育逐渐成熟,Ⅰ型肺泡细胞逐渐增多。结论 在人胎肺的发育过程中,Ⅱ型肺泡细胞的出现并不明显早于Ⅰ型肺泡细胞,原始肺泡上皮所衬的较幼稚的细胞,可能是成熟肺泡上皮细胞的干细胞或祖细胞,Ⅰ型肺泡细胞的出现是胎肺开始具有换气功能的标志,32周时换气功能趋于完善。

Electron microscopic observations of alveoli development and epithelial differentiation in the fetal lung of the Chinese

Objective To observe the development of the a lv eoli and the differentiation of the epithelium in the fetal lung of Chinese.Methods Chinese human lung tissues were obtained from 20 fetuses of 10 to 34 weeks old, and the ultrastructural changes of the alveolar epithelial cells were obs erved using both optical and transmission electron microscope.Results At the f irst 10 to 16 weeks of development, the lung showed a tubular structure, the epi thelial cells were columnar and poorly differ-entiated. At weeks 17 to 24, the b ronchioles increased and the epithelial cells were differentiated to approach ma turity. A few lamellar bodies were observed in the cuboidal lining cells with t he majority being type Ⅱalveolar cells at 25 weeks, when the primitive alveola r was formed. In this stage many primitive epithelial cells could be seen, which appeared primordial in form before evolving into type Ⅱand typeⅠcells and pe rhaps served as epithelial stem cells or progenitor cells. From about 26 weeks, type Ⅰcells were observed but most of the epithelial cells were type Ⅱcells. Type Ⅰcells began to increase in the alveolar epithelium until 32 weeks.Conclusions The alveolar type Ⅱcells and type Ⅰcells are probably both derived from the same precursor cells or stem cells, and no evidence has shown that type Ⅱ cells may differentiate into type Ⅰcells during the development of the fetal l ung.