Chapter 4 - Cleavage & Blastulation Flashcards
The series of divisions of the early embryo which occur within the confines of the zona pellucida.
cleavage or segmentation
Resulting cells from the cleavage segmentation
Blastomeres & Blastoderm
2 types of cleavage
Holoblastic & Meroblastic
- Complete segmentation
- Cells become subdivided completely into blastomeres
Holoblastic cleavage
- Incomplete segmentation
- Only a part of the cell is subdivided into blastomeres
Meroblastic cleavage
Contains a little yolk material that undergo the segmentation division first.
Animal pole
Contains much of the yolk material which is the last to be segmented.
Vegetal pole
Where does segmentation division begin, this is also where the blastodisc or embryonic disc is located?
Animal pole
Ovum with evenly distributed yolk
Isolecithal
ovum in which the yolk is concentrated in the interior of the egg and
the cytoplasm is distributed as a thin coat on the external surface
Centrolecithal
ovum in which the amount of yolk present displaces the embryo forming
cytoplasm into a small area at the animal pole.
Telolecithal
The 1st cleavage furrow divides the cell LONGITUDINALLY into how many equal cells?
2 cells, 2 cell stage
The 2nd cleavage furrow HORIZONTALLY divides the cells into how many equal cells?
4 cells, 4 cell stage
- Ball of cells
- Cellular mass of embryo
- occupies perivitelline space
- means mulberry in Latin
Morula
Result of further cleavage division, a compact mass embryo which occupies 60-70% of perivitelline space is called.
Compacted morula
Form tight junctions destined to become trophoblast or
trophoectoderm
Outer blastomeres
Form gap junctions destined to become inner cell mass
Inner blastomeres
Cavity formed during early blastocyst when fluid accumulates, flattening some blastomeres.
Blastocoele
The future of the outer cells of blastomeres
Trophoblast
The future of the inner cells of blastomere which then becomes the embryonic disc.
ICM or Inner Cell Mass
When the diameter of the embryo dramatically increased with the concurrent thinning of zona pellucida this results to?
Expanded blastocyst
When zona pellucida ruptures, and the blastocyst leaves the zona pellucida and attaches to uterine mucosa this results to?
Hatching blastocyst
How many differentiations will the ICM differentiates into?
2 cell populations
Those facing the blastocyst cavity become flattened and delaminate, forming an
inner cell sheet referred to as the
hypoblast
The remaining cells form the multilayered
epiblast
True or False blastocyst elongation do not vary among species of animals.
False - blastocyst elongation do vary among animals.
What’s the shape of blastocyst elongation for Horses, dogs, cats and rabbits?
Round to oval
What’s the shape of blastocyst elongation for cattle, sheep, pig?
thread-like
True or false there’s little expansion or elongation of blastocyst for primates, rodents, and guinea pigs because of blastocyst invasion on the endometrium.
True
The two regions composing the blastoderm of Avian species.
Area pellucida & Area opaca
A blastoderm region on Avian species consisting of a thin layer of cells and overlies the subgerminal cavity, and with no yolk material attached.
Area pellucida
A blastoderm region on Avian species consisting of a layer of large cells and overlies the unaltered yolk.
Area opaca
Shape of “hatched” blastula for Dogs
Pear-shaped
Hatched blastula shape for Horse
Spherical
Hatched blastula shape for cattle, pig and Sheep
Elongated apprx. 1cm/hr
