EMBRYOLOGY FOR FRESHERS…

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.

Lyse endometrium & burrow in….to keep warm!

Post–Implantation endometrium heals and covers the embryo.

EMBRYOGENESIS 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.

Primitve

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 NIGHT

WE THANK THE VARIOUS SOURCES WE SEMI-STOLE PICTURES AND INFO FROM…FOR ALL REFERENCING QUERIES PLEASE SPEAK TO CRAIG BRAGG!