DONE Embryology Flashcards
What is the pre-embryonic period?
1st 2 weeks of development
- Cleavage (forms morula)
- Compaction (forms blastocyst)
- Implantation
Where is the sperm fertilised?
Ampulla of Fallopian tube
Where is the ideal site for implantation?
Posterior uterine wall
What is cleavage?
In week 1
Mitotic divisions = 2 blastomeres of equal size
Zona pellucida forms
What is a morula?
When compacted blastomeres divide to form 16-cell (each cell totipotent) morula
What is compaction?
In week 1
Formation of 1st cavity + blastocyst
Segregates inner + outer cells
In a blastocyst, after compaction, what is the trophoblast?
Outer cell mass, forms epithelial wall, contributes to placenta
In a blastocyst, after compaction, what is the embryoblast?
Inner cell mass, form embryo
After compaction are the cells pluripotent, totipotent or multipotent?
Pluripotent (can become many cell types)
What is hatching?
Week 1
Blastocyst hatches from zona pellucida after compaction for implantation
How many cells does the blastocyst have at start of implantation?
100 cells, 8 make embryo, rest form fetal membranes
Where does implantation begin?
Blastocyst implants into uterine epithelium (endometrium)
What occurs in the week of twos?
2 cellular layers emerge from the outer cell mass + inner cell mass
In the week of twos what does the outer cell mass form?
Syncytiotrophoblast = multi-nucleated epithelial, transport between mother + embryo Cytotrophoblast = inner layer mononucleated cells
In the week of twos what does the inner cell mass form?
The bilaminar disc:
- Epiblast = columnar cells next to amniotic cavity
- Hypoblast = cuboidal cells next to blastocyst cavity
