Cleavage, Morula, and Blastocyst Formation Flashcards
Once the zygote has reached the two-cell stage, it undergoes a series of mitotic divisions, increasing the numbers of cells. These cells, which become smaller with each cleavage division, and are known as ………
Blastomeres
Until the ……………cell stage, blastomers form a loosely arranged clump
eight-cell stage
3 days after fertilization, cells of the compacted embryo divide again to form a ……………
16-cell morula
Define the process of compaction
After the third cleavage, blastomeres maximize their contact with each other, forming a compact ball of cells held together by tight junctions.
Compaction segregates inner cells, which communicate extensively by gap junctions, from outer cells.
…………….. segregates inner cells, which communicate extensively by gap junctions, from outer cells.
Compaction
The morula is formed ……….. days after fertilization
3 days
The trophoblast is formed by the…………..
Outer cell mass
How is the blastocoele formed?
About the time the morula enters the uterine cavity, fluid begins to penetrate through the zona pellucida into the intercellular spaces of the inner cell mass. Gradually, the intercellular spaces become confluent, and finally, a single cavity, the blastocele, forms.
Trophoblastic cells over the embryoblast pole begin to penetrate between the epithelial cells of the uterine mucosa on about the ……… day
6th day
What are the developmental changes a human zygote has passed through by the end of the first week?
By the end of the first week the human zygote must have passed through morula and blastocyst stages, and has begun implantation in the uterine mucosa
Embryonic stem cells are derived from ……………
the inner cell mass of the embryo
The zygote reaches the 2 cell stage …….. hours after fertilisation
30 hours
When is the morula formed?
3 days after fertilisation
The four cell stage is formed at about ……. after fertilisation
40 hours
When is the late morula formed?
4 days after fertilization
Fluid enters the intercellular space of the inner cell mass through …………
The zona pellucida
The side of attachment of embryoblast is called ……….. while the opposite side is ………..
The side of attachment of embryoblast is called embryonic pole while the opposite side is abembryonic pole
………. prevents the embryo from sticking to the uterine tube
Zona pellucida
the trophoblast differentiates into 2 layers on day ……
Day 8
The embryoblast differentiates into 2 layers on day …….
Day 8
The embryoblast also differentiates into 2 layers namely;
Hypoblast and epiblast
The trophoblast differentiates into two layers namely;
cytotrophoblast and syncytiotrophoblast
How is the amniotic cavity formed?
A small cavity appears within the epiblast, and the cavity enlarges to form the amniotic cavity
……….. cells line the amniotic cavity.
Epiblast cells
Trophoblast is characterized by villous structures by day ……
Day 13
