Traditional nuclear segmentation method

Pancreatic enzyme digestion is used in blastomeres because the blastomeres obtained by digestion have the ability to develop into embryos independently in vitro. After the blastocyst stage, even if it is digested by trypsin, the digested single cells cannot develop into embryos in vitro (and the cells in the blastocyst stage are very closely connected, so it is difficult for trypsin to separate them). Therefore, mechanical separation with a dividing needle will generally divide all parts of the embryo equally, including the outer trophoblast and the inner cell mass. Only in this way can the separated parts form a complete embryo in vitro and then develop into individuals.

This is why there is no need for endoderm when trypsin is used for cleavage.