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Embryology For Freshers …. The Embryonic Period. 1 st 8 weeks worth of growing and changing Split into 23 stages (We don’t know them all!!!) Lets take just 3…. Pre-implantation Implantation of Blastocyst Embryogenesis (Making the baby). Pre - Implantation.
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The Embryonic Period • 1st 8 weeks worth of growing and changing • Split into 23 stages (We don’t know them all!!!) • Lets take just 3…. • Pre-implantation • Implantation of Blastocyst • Embryogenesis (Making the baby)
Pre - Implantation • Fertilization – Form a zygote (Stage 1 Day 1) • Clevage – cell proliferation via number of mitotic divisions…2,4,6,8 daughter cells called blastomeres collectively called a Morula (Day 2-3) • This Morula is the same size as the original zygote but with all those extra cells squeezed in! • All the while cilia are pushing us along the tubes…
Pre-Implantation continues… • Differention of inner load of cells – Blastocyst (Days 4-5) • Trophoblast – outside layer which differentiate into… • Syncytiotrophoblasts and Cytotrophoblasts • These two will go wild invading the mothers uterus becoming the placenta whilst the blastocyst becomes the embryo proper…but that’s later!! • Blastocyst attaches (Day 6)
Implantation (Week 2…week 2 of the 2s) • It’s the 2nd Phase of the embryonic period • 2 trophoblastic layers (Syncytio & Cyto • Embryo becomes bilaminar (2) layered disc • 2 extraembryonic vesicles (Amniotic Cavity and Yolk Sac)
Still the week of the 2’s • Syncytiotrophoblasts (I think Sin City and of it all kicking off and invasions etc) release lysosomal enzymes. • Lyseendometrium & burrow in….to keep warm! • Post–Implantation endometrium heals and covers the embryo.
Embryogenesis • The epiblastinvaginates becoming the ectoderm • This invagination displaces the hypoblasts which become the endoderm • Meanwhile…back in the middle the mesoderm sneaks in there! • These 3 layers proliferate, migrate and differentiate to produce tissues and organs of developing embryo.
What the germinal layers do… • Ectoderm – Cells of Nervous system & Skin • Mesoderm – Muscle & Bone tissue • Endoderm – Inner lining of visceral organs… GI and all that jazz!
Thank you & Good nightWe thank the various sources we Semi-Stole pictures and info from…For ALL referencing queries please speak to Craig Bragg!