These epithelial elements arise embryologically from foregut endoderm in the process of bronchial tubular growth . 这些表皮细胞在胚胎学上把源于支气管生长过程中的前内脏叫内胚层。
2.
The astrocyte marker gfap and oligodendrocyte marker mbp were not detected . nor the endoderm and mesoderm markers 胶质细胞标志基因gfap 、 mbp未检测到，其他胚层的标志性基因也没有表达。
3.
These congenital lesions arise from abnormal separation of the endoderm and neuroectoderm during embryogenesis 这些先天性的异常是因为再胚胎发育时，内胚层与神经外胚层不正常的分离所造成的。
4.
Whole mount in situ hybridization showed that amphihmgb transcripts were present ubiquitously in the early embryos from zygote to neurula , but they decreased gradually in mesoderm and endoderm and neural tube with development , and became restricted to epidermal cells in the hatched larva . it appear s that hmgb plays a role in the mitosis and differentiation of embryonic cells . another amphioxus cdna , amphiubf80 , encoding ubiquitin / ribosomal fused protein s27a , was isolated from the gut cdna library of b . belcheri tsingtauense S004cdna序列编码一个156个氨基酸残基组成的蛋白质，与人的泛素蛋白ubf80具有较高的氨基酸序列同源性( 145 / 156同源) ，且该蛋白具有泛素蛋白ubf80所共有的两个结构域，即由72个氨基酸组成的泛素介导的蛋白降解结构域和由48个氨基酸组成的核糖体蛋白s27a结构域。
5.
Ranging from 100 to 200 microns across , the width of several human hairs , these microscopic fossils are surprisingly complex and constitute almost a textbook example of a bilaterian , including the three major tissue layers ( the endoderm , mesoderm and ectoderm familiar from high school biology texts ) , the presence of a gut with a mouth and anus , and paired coeloms ( body cavities ) surrounding the gut 这些微化石的大小为100 ~ 200微米，相当于几根头发的宽度， ?们看起来出奇复杂，而且简直就像两侧对称动物的教科书般，展示了各种特徵：包括三个主要的组织层（内胚层、中胚层及外胚层，都是中学生物课本中熟悉的名词） ，前后连接口部与肛门的肠腔，肠腔外还围绕著成对的体腔。
