The dorsoventral polarity of Drosophila egg is established by means of signaling between the germ line-derived oocyte and the surrounding somatic follicle cells.

果蝇胚胎是由四种系统，分别控制头尾、前、后以及背形成。

In the posterior segment, its dorsoventral axis was the longest, and could be divided into two parts: the dorsal and the ventral parts.

后段背长，可分为背侧和侧，两分细胞分界清晰。