Embryology (2)

Describe the overall process of early embryonic development, including cell division of the fertilized oocyte (Slides, p. 4), formation of the blastula (video Embryonic Development), and gastrulation (Slides, p. 9). Some important terms that you will learn include oocyte, sperm, fertilization, zygote, cleavage, morula, blastocyst, trophoblast, cytotrophoblast, syncytiotrophoblast, chorion, placenta, inner cell mass (embryoblast), bilaminar disc, epiblast, amnion, and hypoblast.

1. oocyte and sperm undergo fertilization (come together) to make a zygote
2. Zygote undergoes cell division called cleavage
3. Around 16 cells, it will be known as a morula
4. keeps undergoing cell division until 100 cells which is called a blastocyst
5. 2 parts of the blastocyst are the trophoblast and the embryoblast/inner cell mass
5. the trophoblast becomes the chorion which is the fetal portion of the placenta
6. the inner cell mass becomes the embryo
7. During implantation, trophoblast becomes the syncytiotrophoblast, which helps blastocyst burrow into the uterine wall with its nutrient enzymes, and cytotrophoblast, which maintains the outer structure outside the epiblast cells
8. During implantation, inner cell mass becomes the 2 layers: epiblast, which lines the amnion cell, and hypoblast, which lines the yolk sack

Three prenatal periods (with weeks)

• Pre-embryonic period (weeks 1-2)

• Embryonic period (weeks 3-8)

• Fetal Period (weeks 9-38)

Pre embryonic period order

zygote, cleavage (16 cells) into morula, blastocyst (100 cells)

what does the trophoblast become

Becomes the chorion which is the fetal portion of the placenta

inner cell mass (embryoblast) becomes what

embryo

trophoblast becomes what during implantation

syncytiotrophoblast andcytotrophoblast

syncytiotrophoblast

helps blastocyst burrow into the uterine wall with its nutrient enzymes

cytotrphoblast

maintains the outer structure outside the epiblast cells

inner cell mass becomes what 2 layers

epiblast and hypoblast

epiblast

lines the amnion cell

hypoblast

lines the yolk sack