Gastrulation Cut edge of amnion Migrating epiblasts will form X-section at"B Primitive streak Cloacal membrane Endoderm(内胚层): migrated cells displace hypoblast cells Mesoderm(中胚层): cells btw the endo and ector voblasts Ectoderm(外胚层) (Note-epiblasts=>all layers) Invaginating mesoderm colls Mesoderm cranial and lateral extension fused membranes Oral: oropharyngeal membrane(口咽膜) Cloaca!: cloacal membrane(泄殖腔膜) Cloven membaneGastrulation •Migrating epiblasts will form: -Endoderm（内胚层）: migrated cells displace hypoblast cells -Mesoderm（中胚层）: cells btw the endo and ecto -Ectoderm（外胚层） (Note - epiblasts=>all layers) •Mesoderm cranial and lateral extension •Fused membranes –Oral: oropharyngeal membrane（口咽膜） –Cloacal: cloacal membrane（泄殖腔膜）