18 Embryology (Embryonic Phase)

Question 1

What are the key events of the embryonic phase?

Answer 1

Implantation and bilaminar disc formation
Gastrulation
Neuralation

Question 2

What is the timeline of the embryonic phase?

Answer 2

weeks 2-8

Question 3

What occurs in the implantation phase?

Answer 3

the morula implants into the uterine wall in week 2

during implantation the morula forms a bilaminar embryonic disc:

upper epiblast becomes primary germ layers

hypoblast forms extraembryonic tissue

Question 4

What occurs in the gastrulation phase?

Answer 4

occurs in week 3

Primitive streak develops

Notochord develops (thickening of mesodermal cells beneath primitive streak)

formation of primary germ layers:

ectoderm
mesoderm
endoderm

Question 5

what occurs in the neuralation phase?

Answer 5

the embryo develops a brain and spinal cord

chemical signals from notochord initiate neuralation

neural plate forms over notochord

ectoderm folds inward as neural groove

neural folds fuse and form neural tube

neural tube pinches off from ectodermal layer