Flashcards in Reproduction Final Part 3 (Pozor) Deck (33):
Name a major function of the utero-tubal junction.
Delays capacitation until ovulation
T/F: In the presence of progesterone, sperm storage is not necessary and may be eliminated.
Changes that must occur in sperm before they are able to attach and penetrate an ovum.
Name some changes that occur during capacitation.
-Loss of membrane cholesterol
-Increase in pH
-Changes in intracellular Ca++
-Activation of protein kinase A
-Polymerization of globular actin to filamentous actin
Name some important molecules found in oviductal fluid.
An O-linked oligosaccharide attached to a ZP3 protein appears to be directly related to what?
What glycoprotein is the sperm receptor?
What occurs in secondary binding of sperm?
Sperm bind to ZP2 receptors on the inner acrosomal membrane. This allows sperm to travel through the zona pellucida.
Name a believed function of hyaluronidase.
Dissolve the hyaluronic acid complex matrix of cumulus cells surrounding the oocyte.
What two major steps must a sperm complete to be able of fusing with the plasma membrane of an oocyte?
-Penetration of the zona pellucida
Describe the significance of the sperm equatorial segment.
This part of the sperm fuses with the egg plasma membrane.
Describe the "slow block".
Once a sperm has successfully fused with an oocyte, there is an immmediate increase in intracellular Ca++, which causes cortical granule exocytosis. This causes the oocytes coat to toughten and deactivate both ZP3 and ZP2 glycoproteins.
Describe the "fast block".
When a sperm fuses with the vitteline membrane and there are changes in membrane polarization which inhibits fusion by other sperm.
Describe the formation of the female pronucleus.
After a sperm has fused, the oocyte reacts to the rising intracellular levels of Ca++ by completing meiosis II and surrounding the non-polar body by a nuclear membrane.
Describe the formation of the male pronucleus.
Once paternal chromatin is exposed directly to ooplasm, decondensation occurs and a new nuclear membrane is formed.
The products of conception, including the embryo, the extraembryonic membrane and the placenta.
An early embryo consisting of an inner cell mass, a blastocoele, and a trophoblast.
What hormones control luteolysis?
Describe the hormonal activation of luteolysis.
-Oxytocin binds to receptors in uterus and stimulates pulsations of prostaglandins.
-During early diestrus progesterone blocks formation of oxytocin receptors in uterus.
-Therefore, this process only occurs late in diestrus when progesterone levels are failing.
-Once the pulses of prostaglandin begin, they grow until they reach a critical point at which time luteolysis begins.
When the entire uterus is removed (in any species except the primates), what effect is had by the CL?
CL lifespan is prolonged much like gestation.
When the uterine horn contralateral to the CL is removed, what effect is had by the CL?
When the uterine horn ipsilateral to the CL is removed, what effect is had by the CL?
CL lifespan is moderately prolonged
How does prostaglandin get from the uterus to the CL?
Through a countercurrent exchange mechanism.
-Two vessels travel closely to one another, but in opposite directions.
-Small molecules can travel from one to another if there is a concentration gradient.
-Prostaglandin is released from the endometrium and enters the utero-ovarian vein.
-After entering the vein, prostaglandin can switch over to the utero-ovarian artery and travel directly to its destination.
What happens if a female doesn't recognize pregnancy?
-Female returns to estrus
Describe how the horse conceptus is different in its method to achieve contact with the uterine epithelium.
Whereas most mammals grow to create ample surface area of contact, the horse remains small. To accommodate, the horse travels throughout the uterus to contact as many places as possible.
What hormone must conceptuses interfere with in order to prevent luteolysis?
How do ruminants alert the mother of pregnancy?
They use a protein called interferon-tau (INF-tau) which acts on the endometrium to downregulate the synthesis of estrogen receptors. This, in turn, inhibits synthesis of oxytocin receptors. No oxytocin signals = no prostaglandin pulses = no luteolysis.
How do pigs alert the mother of pregnancy?
Estrogen is produced by the conceptus which alters the direction of prostaglandin secretion and prevents luteolysis by preventing prostaglandin from gaining access to the CL.
What happens if there are at least two conceptuses per horn in a pig, will there be recognition of pregnancy?
-Each conceptus produces estrogen.
-2/horn produce enough estrogen to signal the endometrium
-Once signaled, the endometrium secretes the prostaglandin intrauterine where it is sequestered.
-Recognition is achieved.
What happens if there are less than two conceptuses per horn in a pig, will there be recognition of pregnancy?
-Each conceptus produces estrogen.
-<2/horn does not produce enough estrogen to signal the endometrium
-Without signalment, the endometrium secretes the prostaglandin into the ovaries where luteolysis occurs.
-Recognition is not achieved.
How do horses alert the mother of pregnancy?
-The conceptus is small and does not grow rapidly
-Instead, conceptus migrates throughout uterus to achieve maximum contact.
-Endometrium is signaled by migrating conceptus and reduces production of prostaglandin.
How do dogs alert the mother of pregnancy?
The CL lifespan in pregnant bitches and non-pregnant bitches is the same, which is long enough to not need signalment as progesterone is naturally sufficient.