the process of gastrulation. remnant of blastocoel, invaginating, endoderm, ectoderm,

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