What is the process involving cell rearrangements to form the three primary germ layers?
During gastrulation in embryonic development, cells undergo rearrangements to form the three primary germ layers (ectoderm, mesoderm, endoderm). This process involves invagination, ingression, and delamination of cells. Invagination occurs when cells move inward, ingression refers to individual cells leaving the surface epithelium and entering the interior, and delamination involves cells moving between epithelial layers. Together, these movements help establish the three germ layers that give rise to different tissues and organs in the developing embryo.