Cardiac Embryology (Part 1): Topic 5 Flashcards
Where does fertilization occur?
Ampullary region of the fallopian tube
What forms a zygote?
Sperm + Oocyte
What undergoes cell divisions?
Zygote
When does the embryo reach the 2 cell stage?
30 hours post fertilization
When does the embryo reach the 4 cell stage?
40 hours post fertilization
When does the embryo reach the 12-16 cell stage?
72 hours (3 days) post fertilization
Describe the series of mitotic division that occurs.
Cells increase in number
Become smaller with each division
What are the cells called after cleavage of the zygote during mitotic cell divisions?
Blastomeres
Cells are loosely arranged until what stage?
8 cell stage
After which cleavage do cells have maximized contact with each other?
After the 3rd cleavage
What is compaction?
Cells separate into inner and outer cells
What is the 16 cell stage called?
Morula
Describe the Morula.
16 cell stage
Had defined inner and outer cells
Inner cells = inner cell mass (embryo)
Outer cells = outer cell mass (trophoblasts, which will be the placenta)
What cells will become the placenta?
Trophoblasts
What will the inner cells of the morula become?
Embryo
What will the outer cells of the morula become?
Trophoblasts, which will become the placenta
What happens to the Morula?
Makes its way into the uterus, enlarges and becomes a blastocyst
The first cleavage is completed about how many hours after fertilization?
30 hours
Morula develops how many days after fertilization?
3-4 days after fertilization
When does the blastocyst form?
4.5-5 days after fertilization
When does implantation occur?
About 6 days after fertilization
Fertilization occurs how many hours after ovulation?
12-24 hours after ovulation
What happens when the morula enters the uterine cavity?
Fluid penetrates into the intercellular spaces of inner cell mass. Space becomes a single cavity called the blastocele
Blastocele
Single cavity that is formed when fluid penetrates into the intercellular spaces of inner cell mass when morula enters the uterine cavity
Internal fluid filled space
What is the blastocyst comprised of?
Trophoblast
Blastocele
Embryoblast
Trophoblast
Outer covering; formed form cells of the outer cell mass. Cells flatten and eventually form the epithelial wall of the blastocyst; will be come the placenta
Embryoblast
Inner cell mass; located at one pole
How long does the blastocyst remain free in the uterus?
2 days
When does implantation occur?
Day 6 after fertilization
Trophoblastic cells over the embryoblast pole penetrates between what?
Epithelial cells of the uterine wall
Blastocyst attaches to the uterine epithelium and subsequently what? How is it oriented?
Endometrium; oriented os the inner cell mass is near the endometrium
What is the sequence of events for implanation?
- Trophoblast cells over embryoblast pole penetrate between epithelial cells of uterine wall
- Blastocyst attaches to uterine epithelium and subsequently the endometrium
- Oriented so the inner cell mass is near the endometrium
At what day is the Blastocyst partially embedded?
At day 8
What are the two layers that the trophoblast cells over the embryoblast differentiate into?
- Syncytiotrophoblast
2. Cytotrophoblast
Syncytiotrophoblast
One of the two layers that the trophoblast cells over the embryoblast differentiate into; multi-nucleated, outer zone (no cell boundaries)
Cytotrophoblast
One of the two layers that the trophoblast cells over the embryoblast differentiate into; mononucleated cells, inner layer (distinct cells)
What do the two layers that the trophoblast cells over the embryoblast become part of?
Part of the chorion (one of the fetal membranes)
What does the inner cell mass (embryoblast) differentiate into?
Hypoblast layer
Epiblast layer
Hypoblast layer
Layer of small cuboidal cells adjacent to the blastocyst cavity; one of two layers that the inner cell mass (embryoblast) differentiates to
Epiblast Layer
Layer of high columnar cells adjacent to amniotic cavity; one of the two layers that the inner cell mass (embryoblast) differentiates to