Does chicken embryo form the disc called "discoblast" in the cleavage and blastulation of chicken? This thread is related to my previous thread which is still unsolved mainly. I need to be able to compare chick and human cleavage and blastulation of zygote. My friend says that > Chicken have discoblast, human not. That is the main thing to get the idea of the difference. I know that chicken have yolk sac with yolk, while human have yolk sac without yolk. My notes say that > Cleavage in birds is partial discoidal (embryo forms disc and cells called blastodisc are on top of the yolk). So embryo forms some disc, lets call it #1. Some cells called blastodisc are on top of the yolk. **So are the cells called blastodisc on top of the yolk and the disc #1?** **What is the name of the given disc that chick embryo forms?** It seems that human is not forming the given disc. Apparently, the name of the given disc is discoblast, the thing he says is very important.

It is a mnemonic of two words: discoidal + blastula = discoblastula. So it suggests that cleavage is partial discoidal in birds. Embryo forms disc. Cells called blastodisc are on top of the yolk. It seems that the formed disc is blastodisc.