摘要
对3～22周龄山羊胎儿肺进行了肉眼、光镜和透射电镜观察,结果表明:1.7～22周龄山羊胎儿肺的外部形态与胎龄无关,肺的外部形态以左二右四叶者为多见,肺的叶间裂和右肺副裂常不完整,以浆膜、肺组织或混合性组织(肺组织及浆膜)融合;2. 山羊胎儿肺的发育分为5个时期:胚胎期(3～5周) 肺芽分支形成主支气管,主支气管长度不断增长并萌芽出叶支气管,均衬以假复层柱状上皮.腺状期(6～12周) 以支气管树发育为主,小支气管衬以假复层和/或单层柱状上皮;终蕾呈腺状,上皮细胞由假复层柱状逐渐变为单层柱状,胞核向细胞顶端移行;终蕾上皮细胞游离面可见短小的微绒毛;线粒体、粗面内质网及核糖体随着胎龄增加而逐渐增多,它们均位于细胞顶部.小管期(13～14周) 以呼吸部发育为主,原始肺泡开始形成,呼吸性细支气管衬以未分化的立方上皮;终蕾腺状结构逐渐消失,终蕾上皮细胞由高矮不等的单层柱状上皮逐渐演变为立方形的原始肺泡上皮;细胞游离面可见较多的微绒毛,胞质内线粒体、粗面内质网及核糖体较发达.囊状期(第15周) 呼吸部发育显著,肺内细支气管及其末端呈现出'充气'状态;部分原始肺泡上皮细胞分化为扁平的肺泡Ⅰ型细胞和立方形的肺泡Ⅱ型细胞;Ⅱ型细胞内出现嗜锇小体.肺泡期(16～22周) 以肺泡的形成和分化为主,更多的肺泡上皮分化为扁平的肺泡Ⅰ型细胞和立方形的肺泡Ⅱ型细胞.此期,毛细血管内皮与部分肺泡上皮贴近,可将肺泡上皮细胞区分为3种:Ⅰ型细胞,呈矮柱状或椭圆形,胞质中有较明显的核糖体、扩张内质网及变性线粒体;形成了由Ⅰ型细胞-基膜-内皮细胞组成的气血屏障.Ⅱ型细胞,胞质内含丰富的嗜锇板层小体和核糖体,内质网扩张呈大小不一的泡状,多泡体出现,线粒体膨大变性,细胞游离面可见少数微绒毛.Ⅲ型细胞,为未分化细胞,呈立方形,胞体较小,胞核相对较大,呈圆或椭圆形,胞质少,呈带状,电子密度低,细胞器少.
Lungs of prenatal goat(3~22 weeks) were observed with eyes,LM and TEM,the results are as following: 1. The 7~22 weeks goat fetal lungs have the same outer appearance which have no relationship with its age. The left lung have two lobes and most of the right lung have four lobes .Most fissures are incomplete which are connected with lobes by lung tissure and/or serosa tissure.2. The lungs of prenatal goat have five stages during their development: (1) Embryologic stage(3~5 weeks) : The lung bud branching and forming into the two principal bronchi, the principal bronchi increase in length and budding lobar bronchi lined with pseudostratified columnar epithelium.(2) Pseudoglandular stage(6~12 weeks): The bronchial divisions were differentiated and their air conducting system became established, lined with pseudostratified and/or single-walled columnar epithelium. The terminal bud assumes a glandular aspect. The terminal bud epithelium were differentiated from pseudostratified columnar epithelium into single-walled columnar epithelium. The nuclei transfer to the top of the epithelial cells gradually. Short and small microvilli appeared on the luminal surface of the epithelial cells. Mitochondria, rough endoplasmic reticulum and ribosomes are all in the top of the cells and increased in number with the development of the lungs.(3) Canalicular stage(13~14weeks):The respiratory bronchioles developed quickly,the primitive alveoli had developed, the respiratory bronchioles were lined by cuboid cells. The terminal buds’ glandular structures disappeared gradually, the respiratory bronchioles and primitive alveoli epithelium were differentiated from single-walled columnar epithelium into cuboid epithelium. More short and small microvilli appeared on the luminal surface of the epithelial cells. Mitochondria, rough endoplasmic reticulum and ribosomes developed dramatically in the cells. (4) Saccular stage (15 week): The respiratory divisions developed dramatically, the lung assumes a more “aerated” appearance, i.e. the prospective air space volume increases relate 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.(5) Alveolar stage (16~22 weeks): The alveoli developed dramatically, more alveoli epithelium differentiated into flattened(type I cell)and cuboid (type II cell)epithelial cells.During this stage, the capillary endothelium were pressed close to some of the alveolar epithelium. The alveolar epithelial cells can be divided into three types as follow: Type I alveolar cells,assumed short columnar or ellipse aspect.Ribosomes,expanded rough endoplasmic reticulum and denatured mitochondria are prominent in the cytoplasm. The blood-air barrier was composed of type I cell,basement membrane and endothelium. Type II alveolar cells: The osmiophilic lamellar bodies and ribosomes are seen abundantly,rough endoplasmic reticulum pools expand and multivesicular bodies are observed. Mitochondria denatured, microvilli of the epithelial cells appear on the luminal surface. The third type of cells are undifferentiated cuboid epithelium, they are small while the nuclei are large relatively. The cells have round or ellipse nuclei, less cytoplasm and little organelles.
出处
《畜牧兽医学报》
CAS
CSCD
北大核心
2005年第2期158-165,共8页
ACTA VETERINARIA ET ZOOTECHNICA SINICA
基金
国家"863"基金项目(39830280)
