Reproduction Final Part 3 (Pozor)

Question 1

Name a major function of the utero-tubal junction.

Answer 1

Delays capacitation until ovulation

Question 2

T/F: In the presence of progesterone, sperm storage is not necessary and may be eliminated.

Answer 2

TRUE

Question 3

Define: Capacitation

Answer 3

Changes that must occur in sperm before they are able to attach and penetrate an ovum.

Question 4

Name some changes that occur during capacitation.

Answer 4

• Loss of membrane cholesterol
• Increase in pH
• Changes in intracellular Ca++
• Activation of protein kinase A
• Polymerization of globular actin to filamentous actin

Question 5

Name some important molecules found in oviductal fluid.

Answer 5

• Albumin
• NaHCO3
• Ca++

Question 6

An O-linked oligosaccharide attached to a ZP3 protein appears to be directly related to what?

Answer 6

Sperm-binding specificity

Question 7

What glycoprotein is the sperm receptor?

Answer 7

ZP3

Question 8

What occurs in secondary binding of sperm?

Answer 8

Sperm bind to ZP2 receptors on the inner acrosomal membrane. This allows sperm to travel through the zona pellucida.

Question 9

Name a believed function of hyaluronidase.

Answer 9

Dissolve the hyaluronic acid complex matrix of cumulus cells surrounding the oocyte.

Question 10

What two major steps must a sperm complete to be able of fusing with the plasma membrane of an oocyte?

Answer 10

• Acrosome reaction

- Penetration of the zona pellucida

Question 11

Describe the significance of the sperm equatorial segment.

Answer 11

This part of the sperm fuses with the egg plasma membrane.

Question 12

Describe the “slow block”.

Answer 12

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.

Question 13

Describe the “fast block”.

Answer 13

When a sperm fuses with the vitteline membrane and there are changes in membrane polarization which inhibits fusion by other sperm.

Question 14

Describe the formation of the female pronucleus.

Answer 14

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.

Question 15

Describe the formation of the male pronucleus.

Answer 15

Once paternal chromatin is exposed directly to ooplasm, decondensation occurs and a new nuclear membrane is formed.

Question 16

Define: Conceptus

Answer 16

The products of conception, including the embryo, the extraembryonic membrane and the placenta.

Question 17

Define: Blastocyst

Answer 17

An early embryo consisting of an inner cell mass, a blastocoele, and a trophoblast.

Question 18

What hormones control luteolysis?

Answer 18

• Prostaglandin
• Oxytocin
• Progesterone

Question 19

Describe the hormonal activation of luteolysis.

Answer 19

• 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.

Question 20

When the entire uterus is removed (in any species except the primates), what effect is had by the CL?

Answer 20

CL lifespan is prolonged much like gestation.

Question 21

When the uterine horn contralateral to the CL is removed, what effect is had by the CL?

Answer 21

No effect.

Question 22

When the uterine horn ipsilateral to the CL is removed, what effect is had by the CL?

Answer 22

CL lifespan is moderately prolonged

Question 23

How does prostaglandin get from the uterus to the CL?

Answer 23

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.

Question 24

What happens if a female doesn’t recognize pregnancy?

Answer 24

• Luteolysis occurs
• Progesterone declines
• Female returns to estrus

Question 25

Describe how the horse conceptus is different in its method to achieve contact with the uterine epithelium.

Answer 25

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.

Question 26

What hormone must conceptuses interfere with in order to prevent luteolysis?

Answer 26

Prostaglandin

Question 27

How do ruminants alert the mother of pregnancy?

Answer 27

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.

Question 28

How do pigs alert the mother of pregnancy?

Answer 28

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.

Question 29

What happens if there are at least two conceptuses per horn in a pig, will there be recognition of pregnancy?

Answer 29

• 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.

Question 30

What happens if there are less than two conceptuses per horn in a pig, will there be recognition of pregnancy?

Answer 30

• 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.

Question 31

How do horses alert the mother of pregnancy?

Answer 31

• 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.

Question 32

How do dogs alert the mother of pregnancy?

Answer 32

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.

Question 33

How do cats alert the mother of pregnancy?

Answer 33

• The CL lifespan in pregnant queens and non-pregnant queens is the same, which is long enough to not need signalment.
• Queens are induced ovulators, so they only ovulate if they are bred. If they are not, they enter a short period of post-estrus.
• Prolactin possibly plays a role…?