8 - Embryology I Flashcards
At how many weeks is the:
- Pre-embryonic period?
- Embryonic period?
- Fetal period?
- Pre-embryonic period - first 2 weeks
- Embryonic period - weeks 3-8
- Fetal period - weeks 9-38
Where is the oocyte released and what tube does it travel along?
Released from ovary into fallopian tube
Where does fertilisation occur?
In the ampulla of the fallopian tube
What is a fertilised oocyte known as?
Zygote
Where is the normal site of zygote implantation?
Posterior uterine wall
How long after fertilisation does the first cell division take place?
~30 hours after fertilisation
What is the zona pellucida and what does it do?
Glycoprotein shell around the oocyte
Excludes all other sperms cells upon fertilisation
What is a morula?
- Solid ball of cells resulting from divisions after fertilisation
- All cells are totipotent (can become anything)
What is the next structure to form after a morula? What is this?
Morula forms a blastocyst
- Forms the first cavity
- Hollow structure of cells with an inner cell mass (embryoblast) and outer cell mass (trophoblast)
- Cells are now pluripotent (can become many cell types but not any)
After 1 week, the blastocyst hatches from the ……. …………… so implantation can occur into the uterine epithelium
Zona pellucida
What does the trophoblast (outer) layer of the blastocyst do?
Provides nutrients to the embryo and develops into the placenta
What occurs during implantation?
The blastocyst adheres to the wall of the uterus and invades the endometrium
The trophoblast (outer) layer of the blastocyst separates into two layers. What are they and what do they do?
Cytotrophoblast - inner trophoblast, penetrates the maternal spiral arteries to route blood to the placenta
Syncytiotrophoblast - outer trophoblast, invades the wall of the uterus to establish nutrient flow
The embryoblast (inner cell mass) forms a bilaminar disc. What are the two layers?
- Epiblast
- Hypoblast
What two cavities are formed by formation of the bilaminar disc? Which side is each one on?
Amniotic sac - above epiblast
Yolk sac - below hypoblast
Which of the two layers goes on to form the trilaminar disc? What are the three layers?
The epiblast
- Ectoderm
- Mesoderm
- Endoderm
What are the layers of the trilaminar disc also known as?
Germ layers
What is the process of formation of the trilaminar disc from the bilaminar disc called?
Gastrulation
What structure forms on the surface of the epiblast during gastrulation? What is its purpose?
The primitive streak (beginning at the primitive node)
- Promotes invagination of the epiblast to form the trilaminar disc
What structures of the body are derived from ectoderm?
- Nervous system
- Epidermis
What structures of the body are derived from mesoderm?
- Muscle
- Cartilage
- Bone
- Vasculature
What structures of the body are derived from endoderm?
- Epithelial lining of internal tracts (e.g. GI and respiratory tracts)