1. E MBRYOLOGY F OR F RESHERS …

3. T HE E MBRYONIC P ERIOD 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)

4. P RE - I MPLANTATION 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…

6. P RE -I MPLANTATION 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)

7. I MPLANTATION (W EEK 2… WEEK 2 OF THE 2 S ) It’s the 2 nd Phase of the embryonic period 2 trophoblastic layers (Syncytio & Cyto Embryo becomes bilaminar (2) layered disc 2 extraembryonic vesicles (Amniotic Cavity and Yolk Sac)

9. S TILL THE WEEK OF THE 2’ S Syncytiotrophoblasts (I think Sin City and of it all kicking off and invasions etc) release lysosomal enzymes. Lyse endometrium & burrow in….to keep warm! Post–Implantation endometrium heals and covers the embryo.

11. E MBRYOGENESIS The epiblast invaginates 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.

12. Primitve

13. W HAT 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!

14. T HANK YOU & G OOD NIGHT W E THANK THE VARIOUS SOURCES WE S EMI -S TOLE PICTURES AND INFO FROM …F OR ALL REFERENCING QUERIES PLEASE SPEAK TO C RAIG B RAGG !