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!