Repro 3 Flashcards
Barriers to Sperm Penetration of Ovum
- location of gametes
- cumulus cells (granulosa cells) - species dependent barrier
- zona pellucida
- vitelline membrane (plasma membrane of ovum)
On approach to ovum, the sperm undergoes _________ , which is the activation of the sperm
acrosome reaction
Things that happen in the acrosome reaction (4)
- activates cation channels
- increases Ca2+
- hyperactivates sperm (motility)
- primes sperm for acrosomal exocytosis
Sperm move by two types of movement. What are the movement types?
dancing and dashing
What kind of movement is dancing for sperm?
left and right
What kind of movement is dashing for sperm?
going forward
These females will loose their cumulus cells around their ovum soon after ovulation
- ewe
- cow
- sow
_______ helps sperm transverse the cumulus oophorus and corona radiata
Hyaluronidase
During cumulus penetration, glycodelin-A and -F on sperm surface is displace by ____________
glycodelin-C
Glycodelin-C binds to the _______ region of the sperm
equatorial
_________ promotes the zona binding capacity of the penetrated sperm
Glycodelin-C
Removal of _________ may allow a more efficient zona-induced acrosome reaction to occur on the surface of the zona pellucida
glycodelin-F
__________ is a glycoprotein coat and has three major glycoproteins: ZP1, ZP2, and ZP3
zona pellucida
T/F: Zona pellucida glycoproteins allow some species specificity as ZP is able to recognize the sperm proteins
True
_______ released form acrosome assists sperm penetrating the ZP and acrosome is lost in this process
Proacrosin
Describe Zona Reaction or Zona Block
Once sperm penetrates ZP, ZP changes and prevents additional sperm entry into the ovum
The sperm reaches the vitelline _____ (before/after) the ZP
after
What segment of the sperm fuses with the vitelline membrane, allowing the entire sperm entrance to the ovum?
equatorial segment
Describe Vitelline block
changes of the vitelline membrane to prevent further sperm attachment after the sperm enters the ovum d/t the release of the contents of the cortical granules
T/F: All but the sperm nucleus is degraded in the ovum
True
What does the Vitelline block do?
prevents further sperm attachement
therefore blocks polyspermy
T/F: Polyspermy is non-lethal
FALSE!!!!
Polyspermy is lethal!
The cortical granules release a _______ that hydrolyzes the ZP2 protein to prevent entry of additional sperms
protease
Two scenarios where polyspermy is likely
- artificial insemination
- In Vitro fertilization
What species is highly susceptible to polyspermy, especially when mating is delayed?
pig
The oocyte is in __________ at the time of sperm penetraton
2nd meiotic division (MII)
Spacing of embryos in the pig
distributed in both uterine horns; embryos space themselves uniformly by day 12 of gestation
If a sheep has 2 embryos, how do they space themselves?
one per uterine horn
If a cow has 2 embryos from the same ovary, how will the embryos be spaced?
both in the same uterine horn
Embryos secrete a chemical that leads to the release of ____________ in the very first days of gestation
Early Pregnancy Factor (EPF)
What does early pregnancy factor in the serum of the mother do? (2)
- suppress immune responses in mother
- improve chances of successful “adoption” of viable embryos
Recognition of pregnancy (3)
- Early Pregnancy Factor
- prolong the life of CL beyond diestrus
- obtaining nourishment
How does the presence of a viable embryo prevent regression of the CL?
developing embryo prevents synthesis and release of PGF2-alpha, which prevents CL from regressing
_______ inhibits pulsatile release of PGF2-alpha
Interferon tau
Interferon tau inhibits pulsatile release of PGF2-alpha, however the baseline for PGF2-alpha is increased, How?
PGF2-alpha is released in bulk instead of in spikes
Species with diffuse placenta
pig and horse