Midterm 3 - Lecture 27 Flashcards
1
Q
Where does fertilization and embryonic development occur?
A
In the germinal disk of the yolk
2
Q
Is polyspermy normal in avian fertilization?
A
Yes!
- several sperm penetrate membranes of the germinal disk and form male pronuclei
3
Q
Syngamy
A
- 1 male pronuclei positioned adjacent to the female pronuclei
- 1 male pronuclei fuses with the female pronuclei, forms a zygot and mitotic divisions begin (other male pronuclei do not contribute)
4
Q
At time of laying, how many cells does the embryo contain?
A
- 30,000-60,000 cells = good start on embryonic development before incubation starts
- mitotic divisions
5
Q
What is development dependent on?
A
- incubation temperature (~37.5)
- fertilized eggs can be stored/transported prior to incubation (below 21)
- development in fertilized eggs can be arrested for up to 7 days with little affect on hatchability
6
Q
How long can fertilized eggs be arrested for?
A
up to 7 days with little affect on hatchability
7
Q
What allows for rapid development of the embryo?
A
- readily available nutrients in the egg (yolk sac and albumin)
8
Q
How long after incubation is a beating heart visible?
A
38 hrs
9
Q
Extra-embryonic avian membranes
A
- yolk sac
- amnion
- chorion
- allantois
10
Q
Yolk sac
A
- 1st extra-embryonic membrane to develop
- endoderm surrounds the yolk within the inner shell membrane and is highly vascular
- provides nutrients tot he developing embryo
11
Q
Amnion
A
- developed by 4 days of incubation
- surrounds developing embryo to protect against mechanical damage and dehydration
- provides protein from albumen that enters the amniotic fluid
- formed from the ectoderm, endoderm and mesoderm of the embryo
12
Q
Chorion
A
- develops next to the inner membrane from the ectoderm, endoderm and mesoderm of the embryo in parallel to the amnion
- close relationship with allantois for air and gas exchange (different than mammals)
13
Q
Allantois
A
- developed by day 4 of incubation from the hind-gut of the embryo for waste collection
14
Q
During the last 2 weeks of incubation, what does the chorion and allantois “act” as?
A
- the “lung” of the embryo-exchanging CO2 for O2 coming through the pores of the shell
- by 12 d of incubation, allantois formation and fusion with the chorion is complete
15
Q
What does the yolk provide to fetus?
A
Energy
