Chapter 12 Chickens Flashcards
_______ (Genus species) has long been a favorite organsim for embryology because the are easy to raise and acquire, temp dependent development, and surgical and genetic modification
Gallus gallus
Gallus gallus eggs (chicken) can develop without the shell (_______)
ex ovo
_______ is a small region of cytoplasm sitting on top of a large yolk
blastodisk
Birds undergo _______ cleavage creating a single layered _______
Meroblastic discoidal
blastoderm
Deep cells in the center of the blastodisk die, leaving 1-cell layer which is called the _______
area pellucida
- will form most of the cells of the embryo
Surrounding the area pellucida is a peripheral area with the remaining deep cells called the _______
area opaca
Thin zone between the area pellucida and area opaca is called the _______
marginal zone
At around the time the egg is being laid, there is cell division leading to a _______
layered blastoderm
_______ the upper layer of the blastoderm, will form the embryo of all 3 germ layers
epiblast
- forms over the blastocoel
_______ under the blastocoel, will form the endoderm, extra-embryonic membranes, yolk sac, and connections between the yolk mass and embryo
hypoblast
- endoderm is formed by both epiblast and hypoblast
_______ is analogous to the blastopore lips from amphibians
primitive streak
The primitive streak originates from the _______, which is a thickening of cells at the posterior end of the area pellucida
Koller’s sickle
Cells of the primitive streak converge, forming the _______, which is a depression through which cells pass from the surface of the embryo into deeper layers
primitive groove
_______ forms from anterior thickening of the primitive streak through which the cells enter the embryo to form the notochord and pre-chordal plate
Hensen’s node
The _______ is analogous to the blastopore in amphibians
primitive groove
________ is analogous to the dorsal blastopore lip of amphibians
Hensen’s node
As cells enter the streak they undergo an _______ allowing them to migrate to new positions throughout the embryo
Epithelial to Mesenchymal transition (EMT)
Cells migrate into two deep layers forming the _______ and _______ layers
mesoderm and endodermal
_______ is extended from the anterior following the regression of Hensen’s node
notochord
- laid down in the head to tail (A—–>P) direction
Gastrulation ends with:
1) _______ epiboly covering the entire surface of the large yolk
2) _______ has replaced the hypoblast
3) _______ positioned between them
1) ectoderm
2) endoderm
3) mesoderm
- takes about 4 days
Gastrulation sequence creates a distinct _______ gradient
anterior-posterior
the egg rotates in the hen’s reproductive tract causing the blastoderm to tip to one side, that side becomes the _______
Posterior Marginal Zone (PMZ)
Current evidence suggests that the _______ are functionally equivalent to the amphibian Nieuwkoop center
Posterior Marginal Zone (PMZ)
The entire PMZ zone produces _______, which helps stablize and promote the accumulation of _______
Wnt8
β-catenin
PMZ cells secrete _______ which paired with Wnt8 acts to induce the expression of _______
Vg1
nodal
Nodal is necessary to initiate the formation of the _______
primitive streak
When Henson’s node is its furthest anterior point, _______ is restricted to the left side
Sonic Hedgehog (SHH)
The sonic hedgehog present on the left side activates _______
cerberus
Cerberus activates _______ with the help of BMP’s, which activates _______ TF
Nodal
Pitx2
On the right side:
- SHH transcription is blocked by _______
activin
On the right side:
- ________ and _______ block the expression of Cerberus
Activin and BMP4
Along the notochord and midline there is a gene called _______, which blocks the signaling of Cerberus and BMPs from transiting the midline
lefty
