Lec.6 CLEAVAGE AND BLASTULATION Flashcards
Upon fertilization, meiosis is completed and cell cycle returns to what process?
During the S phase, the zygote will cleave into a ____ embryo.
Each blastomeres have a full copy of the embryonic genome.
mitosis
2-cell embryo
*Blastomere
Here, mitosis occurs almost without ____
The cells become ____ as the original cytoplasm of the zygote is divided into smaller and smaller portions.
These cell divisions are referred to as ____
cellular growth
smaller
cleavages
*Uterine travel
Cleavages begin during the
transport of the embryo through
the ____
At a species-specific stage of
development, the embryo will enter
the ____
oviduct
uterus
After a few cell divisions, the embryo takes the shape of a small ball of cells referred to as a _____
The outer cells will differentiate into an epithelium, attach firmly to each other, and give the embryo a ____ surface
This process is referred to as _____
morula
smoother
compaction
*Morula
The outer cells are now referred to as ____
The firm attachment between neighboring cells of the trophoblast results from specialized intercellular junctions.
In pigs, this occur at the 8-cell stage, in cattle at ____-cell stage.
trophectoderm or trophoblast
16- to 32-cell stage
After compaction, blastulation will be performed by the cell.
A central fluid-filled cavity will be formed within the early embryo.
This process will transform the embryo into a ____
blastocyst
*Blastocyst
Eventually, the inner blastomeres become positioned at one pole of the embryo forming the ____.
Cells of the ICM will form the embryo proper; cells of the trophectoderm will form the ____ part of the placenta.
inner cell mass (ICM)
embryonic part
*Hatching
The blastocyst will gradually expand and will lead to rupture of the ____ This process is also called hatching.
During hatching, the ICM differentiates into two cell populations: those that will be the ____
those that will be the ____
zona pellucida
hypoblast
epiblast
*Inner cell mass
ICM facing the blastocyst cavity become flattened and delaminate, forming an inner cell sheet called the ____
The remaining cells will form the multilayered ____
hypoblast
epiblast
*Inner cell mass
The hypoblast gradually forms an inner lining beneath the epiblast and the trophectoderm.
This will form the ____
In domestic species, the trophectoderm covering the epiblast (known as ____) gradually disintegrates, exposing the epiblast to the uterine environment.
primitive yolk sac
Rauber’s layer
*Inner cell mass
After the loss of Rauber’s layer, the ____ is seen as a circular at first but becoming oval structure.
Together with its underlying hypoblast this structure is called the ____
epiblast
embryonic disc
*Blastocyst
During the formation of the embryonic disc, the blastocyst is still expanding.
Once the disc is formed, the ____ with its underlying hypoblast becomes reshaped and the embryo becomes ovoid.
This process will mark the end of blastulation.
trophectoderm
In the what animals does the process of elongation continues, and the embryo becomes first tubular and later filamentous.
ruminants and pig
