Fertilization Flashcards
Most mammals are born with oogenesis arrested at the ____ ______ stage.
Primary oocyte
*prophase of meiosis 1
Rabbits, ferrets, and hamsters are born with oogenesis arrested at the less developed, ______ stage.
Oogonia
Meiosis is resumed at the time of _____, with an ovulatory surge of ___.
puberty, LH
Stage at which oocyte growth is complete
Antrum formation
The ovulation stage for most mammals is when the oocyte enters the ______ _____ ______.
second meiotic division
Unlike most mammals, the canine oocyte ovulates at ______, before completion of meiosis 1, when it is not yet mature enough to be fertilized.
Prophase 1
Cytoplasmic changes depend on close association between the oocyte and _____ _____ cells.
Corona radiata
The cumulus mass is important for…
communication and response to stilumi
will be shed right before fertilization can take place
Where does fertilization occur?
Ampulla of the uterine tube
Removal of the _____ _____ removes additional chromosomes from the oocyte before fertilization.
Polar body
Area that serves as a sperm reservoir in which sperm are released at intervals during ovulation to increase the chances of fertilization.
Isthmus of the uterine tube
Capacitation
biochemical (not morphological) changes that take place in the female tract before sperm are capable of fertilization
Steps in Capacitation
Changes in membrane cholesterol and glycosaminoglycans
Sperm become capable of undergoing acrosome reaction
Hypermotility
Oocyte receptor expression (allows species recognition)
The acrosome reaction occurs upon contact with the ____ _______ and involves fusing of the sperm plasma membrane with the sperm outer acrosomal membrane.
zona pellucida
The acrosome reaction allows SEQUENTIAL release of what?
acrosomal enzymes
After a sperm cell attaches to and penetrates the zona pellucida, the ____ and ____ membranes fuse.
sperm and oocyte
Specific protein binding site for sperm.
ZP3
Acrosome reaction is _____ dependent.
calcium
When does species recognition first occur?
At binding of sperm with the zona pellicida proteins
Fusion of sperm membrane with the _____ occurs after the acrosome reaction is complete
oolemma (oocyte membrane) (vitelline membrane)
Blocks to polyspermy occur at the zona pellucida by release of oocyte _____ _____ into the perivitelline space.
cortical granules
After _____, the oocyte expels the second polar body.
penetration
The male and female pronuclei have a _____ set of chromosomes and will come together within the ootid.
haploid
The joining of the 2 pronuclei into one diploid cell is called
Syngamy
Early divisions occur by ______, with no increase in size of the cell
cleavage
What happens if polar bodies are not removed from the oocyte?
Incompatible with development. 3n. Can’t do it.
Fertilization and early cleavage takes place where?
uterine tube
As fluid accumulates, the outer cells of the morula become flattened and a cavity known as the ______ is formed.
blastocoele
How long until the zygote reaches the uterus?
cows and most others - 4 days
horses - 6 days
dogs - 8 days
In the equine, the utero-tubal junction is closed to the zygote unless it can produce _____.
PGE2
The inner cell mass forms
the embryo
Cell other than those in the inner cell mass are responsible for forming
the placenta
Only after _________ can formation of extraembryonic membranes occur.
maternal recognition of pregnancy
extraembryonic membranes
yolk sac
amnion
chorion
allantois
Maternal recognition of pregnancy is critical in prolonging the function of the ____ _____.
Corpus luteum
2 strategies of preserving the corpus luteum during pregnancy
Anti-luteolytic: diversion or inhibition of PGF2a
Luteotropic: maintain CL (hCG in humans)
In ruminants, after hatching from the zona pellucida, the blastocyst elongates and contacts the uterine luminal epithelium which induces production of _______.
IFNt (Interferon tau)
IFNt in ruminants is responsible for maternal recognition of pregnancy and inhibits ______.
PGF2a
In swine, maternal recognition of pregnancy is caused by the blastocyst producing ______, which then changes the path of PGF2a to the uterine lumen where it is deactivated.
estradiol
In the equine, the ______ phase requires the embryo to move through both uterine horns several times per day to prevent loss of pregnancy.
mobility
Polysaccharide-rich membrane unique to equids that preserves the round shape of the embryo, and maintains rigidity necessary for uterine migration.
Embryo capsule
the embryo capsule disappears after __ days
23
In Llamas, which uterine horn carries almost all of the pregnancies?
Left
Recognition of pregnancy in the llama involves
Inhibition of PGF2a synthesis or release
Recognition of pregnancy in the dog
Not needed. Diestrus lasts 60 days either way.
Chorionic gonadotropins in the equine
eCG - produced in the endometrial cups
Chorionic gonadotropins in the human
hCG - produced by the endometrium within 48 hours of fertilization
