Well, it was not very hard for me to draw this red blood cell here, it's just an oval, and one reason I draw it like an oval, is that that's basically what it looks like if you look at it.

我可以很容易的画出,一个血红细胞,就画个椭圆足矣,因为它看上去就是这个样子的

耶鲁公开课 - 生物医学工程探索课程节选