The eighth week represents the last phase of the embryonic period. The fingers and toes are still connected with webbing. Through the apoptosis (physiologic, programmed death of cells) that occurs in the ectoderm as well as in the mesoderm that lies below it, this gradually disappears (interdigital necrosis zones [INZ]). They become separated from one another in this way and can lengthen.
The head has risen up and is connected via the neck with the rest of the trunk. The length of the head is still as large as half the entire embryo. The face is well developed. One can already recognize lips and nose, giving the embryo its human appearance.
Eyes and ears have almost developed to their definitive shapes.
A part of the intestines is still found in the proximal section of the umbilical cord (physiologic umbilical hernia).
At around the 56th day one can well distinguish the various features of both the upper and the lower extremities (elbows, fingers, toes). The first movements of the extremities occur at this time. The tail anlage has completely atrophied at the end of the eighth week.
In summary it can be said that at the end of the embryonic period the organogenesis is almost completely finished. The embryo, which originally arose from a single, 0.14 mm sized cell, now consists of millions of cells and measures 30 mm. The outer sexual organs are not yet differentiated enough that one can determine the baby's gender.
During the fetal period growth stands especially in the foreground and no longer the differentiation of the organs, which in some tissues nevertheless continues even after delivery (central nervous system). In the course of the fetal period out of a 30 mm sized embryo a 500 mm sized fetus will come.