One can imagine that when they're inside this tube here, they're still really outside the body.

你可以想到当食物在肠管的时候,实际上还是处在体外的

耶鲁公开课 - 生物医学工程探索课程节选

This tube, this hollow tube, which food passes through is made up of many, many epithelial cells which directly abut one another and would be a flat sheet except that it's rolled up into a tube.

这个管道,这个中空的管道,食物可以穿行其中,而它就是由许多许多上皮细胞构成的,上皮细胞一个连着一个,形成了一个平坦的细胞层,但实际上它们还在肠管中卷成管状

耶鲁公开课 - 生物医学工程探索课程节选

You can see this region here is going to develop into one of the upper limbs, the arms here and the back is different from the front, the spinal cord is developing in the back, whereas, the structures that become our intestinal tract is developing on the other surface.

你能看到这个区域,将会发育成为上肢,这里是手臂,而且身体前后也有不同,脊椎正在后背发育,另外,会成为我们肠管的结构,也在另一个表面发育着

耶鲁公开课 - 生物医学工程探索课程节选