human embryonic development, or human embryogenesis from zygote to gastrula.

medical egg fertility embryo ovum blastoderm division zygote blastopore fertilized gastrula invaginating development biology pregnancy reproductive science blastocyst microscopic endoderm anatomy morula archenteron cell ball embryonic blastula segmentation embryology human early genetic fertilization nucleus health medicine diagram implantation oocyte stage healthy baby illustration growth stem reproduction ovulation symbol ectoderm body