zygote

zygote

1. 2 blastomere zygote

   • 4 blastomere zygote (CONCEPTUS) not an embryo yet
     • early 8 blastomere stage (Totipotent cells)
       • COMPACTION
         • late 8 blastomere stage
           • CONCEPTUAL DIFFERENTIATION
             • 16 blastomere stage = MORULA
               • inner cell mass
                 • EMBRYOBLAST
                   • at 32-64 cells called BLASTOCYST
                     • D5: hatching from zona pellucida
                       • Pre- implantation
                         • IMPLANTATION
                           • apposition
                           • adhesion
                           • invasion
                     • parallel differentiation of flat bilaminar disk
                       • composed of
                         • HYPOBLAST (primitive endoderm)
                         • EPIBLAST (primitive ectoderm)
                           • whitin it arises
                             • AMNIOTIC CAVITY
                 • at EMBRIONIC POLE
               • outer cell mass
                 • TROPHOBLAST
                   • surrounds
                     • BLASTOCYST CAVITY
                       • containing
                         • BLASTOCOELIC FLUID
                       • First hypoblast proliferation :hypoblast cells migrate and line the blasocyst cavity
                         • forming
                           • HAUSER MEMBRANE
                         • that becomes
                           • PRIMARY YOLK SACK
                             • second hypoblast proliferation and migration
                               • causes primary yolk sack detachment from the embryonic disk
                                 • forming
                                   • SECONDARY YOLK SACK
                   • shortly after adhesion, it differentiates
                     • SYNCYTIOTROPHOBLAST
                       • lacunar stage : TROPHOBLAST LACUNAE
                     • CYTOTROPHOBLAST
                       • in between them it forms
                         • EXTRAEMBRIONIC RETICULUM
                           • later replaced by
                             • extraembrionic mesoderm
                               • splits into
                                 • splancnic layer
                                 • somatic layer
                                 • forming
                                   • the CHORION
                                     • will form
                                       • CHORIONIC VILLI
                                         • will form
                                           • The PLACENTA
                               • angioformative tissue
                 • surrounding ABEMBRIONIC POLE
         • First cell differentiation event in mammalian development