SummarySperm FertilizationCleavageZygoteMorulaOvumAmnioniccavityEndometrium(2 W)Ecto+-EpiblastEmbryonicICMBlastocystDiskimplantationEndo---hypoblastCavityYolksacCyto-BasalisTrophoblastCapsularisDecidualSynParietalisSomatopleureExtra-SplanchnopleureEmbryonicmesodermBodystalk
Sperm Ovum Zygote Morula Blastocyst Endometrium Fertilization Cleavage Trophoblast Cavity ICM Decidual Basalis Capsularis Parietalis Embryonic Disk （2 W） CytoSynExtraEmbryonic mesoderm Splanchnopleure Somatopleure Body stalk Amnionic cavity Yolk sac Endo-hypoblast Ecto- Epiblast implantation Summary
5.Trilaminar Germ layers (week3)Formation of primitive streak4561.Primitivestreak023Rostral2.PrimitivenodeaU9epiblastic cells-primitive streak(primitivegroove,primitivenode)
5. Trilaminar Germ layers (Week 3 ) Formation of primitive streak epiblastic cells →primitive streak (primitive groove, primitive node ) 1. Primitive streak 2. Primitive node
Cut edgeofamnionYolk sacPrimitiveEpiblaststreakAmnionCutB-YolkAInvaginatingHypoblastsacPrimitivemesodermcellsPrimitivenodestreakSignificance: 1) determine the middle axis ;2) determine cranial-caudal-axis;3) Induce mesoderm
Significance: 1) determine the middle axis ; 2) determine cranial-caudal-axis; 3) Induce mesoderm Cut
PrimitivenodePrimitivestreakAmniotic cavityEpiblastYolkSacDevelopingHypoblastmesodermalcells? When: By the end of the 3rd Week?What:Formation of the trilaminargermlayers(allfromepiblast)
? When: By the end of the 3rd Week, ?What: Formation of the trilaminar germ layers Epiblast Primitive node Primitive streak Yolk Sac Developing Hypoblast mesodermal cells Amniotic cavity (all from epiblast)
FormationofNotochordCranialcauPrimitivenodeCaudalEpiblastcells-→primitivenode-→notochordal (head)process
Epiblast cells → primitive node → notochordal (head) process Formation of Notochord Primitive node Cranial Caudal