Ex 3 - Physiology of Pregnancy

Question 1

What is embryonic loss? and what is the incidence?

Answer 1

pregnancy loss prior to fetal stage; 2-20%

*conception rates are often very high, but uterine pregnancy rates are much lower –> this suggests that early embryonic loss rates are significant

Question 2

What happens if embryo is lost prior to MRP?

Answer 2

CL regresses at normal time; no delay in return to estrus –> continues to cycle

Question 3

What happens if embryo is lost after MRP?

Answer 3

CL persists (2-3 months); delay in return to estrus –> loss of breeding season for that animal

*can give PGF to cause luteolysis to cause animal to cycle back

Question 4

When do pig embryos enter the uterus?

Answer 4

at ~48 hrs

Question 5

MRP in pigs

Answer 5

embryos migrate throughout uterus beginning on day 8-9 and spread apart –> cross-horn migration occurs –> migration stops at day 12

Question 6

How many embryos are req’d for MRP to occur in PIGS?

Answer 6

at least 4 and at least 1 embryo must be in each uterine horn

Question 7

What are some causes of early pregnancy loss?

Answer 7

maternal age, endometrial/uterine dz, P4 insufficiency, chromosomal abnormalities

others: nutrition, stress, early postpartum pregnancies

Question 8

What is the placental membrane composed of?

Answer 8

maternal and embryonic/fetal components

Question 9

What is the fetal membrane composed of?

Answer 9

only the fetal component

Question 10

How does embryo get nutrients in early pregnancy?

Answer 10

secretions from endometrial glands –> micronutrients –> taken up by trophoblast cells, and eventually by the vascularized yolk sac

“Histotrophic support”

Question 11

How does embryo get nutrients in later pregnancy?

Answer 11

Development of close assoc’d b/w maternal and fetal membranes

“Hemotrophic support”

Question 12

What is implantation/attachment? and when does it occur?

1. pigs
2. sheep
3. cows
4. horses

Answer 12

An interdigitation of placental tissue with endometrium

1. 14-18 days
2. 15-18 days
3. 18-22 days
4. 35-38 days

Question 13

what is the amnion and when does it develop?

Answer 13

membrane directly around fetus; 21 days

Question 14

What is chorioallantois?

Answer 14

outer placental membrane

Question 15

what is blastocoele cavity?

Answer 15

yolk sac –> storage of nutrients for embryonic development

Question 16

What will make up the umbilical cord?

Answer 16

The folds of the amnion and chorioallantois membranes will form the umbilical cord

The yolk sac recedes as the embryo develops –> umbilical cord envelopes and obliterates the yolk sac

Question 17

When can you start to see a fetal heartbeat?

Answer 17

day 25

Question 18

What are the four types of placentas?

Answer 18

1. diffuse
2. cotyledonary
3. zonary
4. discoid

Question 19

Diffuse placenta

Answer 19

*horse and pig

• microcotyledons evenly spread out across the entire placenta
• histotrophic and hemotrophic support occur throughout gestation

Question 20

Cotyledonary placenta

Answer 20

• ruminants

- discrete attachment sites b/w cotyledons (placenta) and caruncles (uterus) –> form placentomes

Question 21

Zonary placenta

Answer 21

• cats and dogs (carnivores)

- contact b/w placenta and endometrium in a band around the fetus

Question 22

Discoid placenta

Answer 22

*primates

Question 23

3 classifications of placentations

Answer 23

1. Epitheliochorial
2. Endothelliochorlal
3. Hemochorial

Question 24

Epitheliochorial

Answer 24

• LA (cattle, sheep, goats, horses)
• 6 layers of separation b/w mom and baby
• all LA neonates are born WITHOUT AB PROTECTION! there is no transplacental transfer of Igs!

***COLOSTRUM is critical!

Question 25

Endotheliochorial

Answer 25

*Cats and dogs (carnivores) - 4 layers of separation b/w mom and baby - some transplacental transfer of Igs **Colostrum is still very important

Question 26

Hemochorial

Answer 26

*Primates and rodents - 3 layers of separation - fetal chorion comes into direct contact with maternal blood **significant transplacental transfer of Igs

Question 27

What are the two sources of P4?

Answer 27

CL and placenta

Question 28

Which spp are CL-dependent for P4?

Answer 28

dogs, cats, goats, camelids

Question 29

Which spp utilize both CL and placenta for P4? and how long is the CL needed?

Answer 29

Horse - 70 days Sheep - 50 days Cows - 6-8mo

Question 30

What are equine endometrial cups?

Answer 30

Specialized trophpblast cells that invade the endometrium at **35 days** of gestation Form distinct "cup-shaped" aggregations of fetal tissue w/in the maternal endometrium

Question 31

What do e-cups produce and secrete?

Answer 31

eCG!! may provide protection from the maternal immune system eCG has both FSH and LH biologic activity

Question 32

FSH in pregnant mares and ecups

Answer 32

Endogenous FSH stimulates follicle development in pregnant mares --> eCH causes ovulation and/or leutinization of large follicles --> secondary/accessory CLs form --> provide additional P4 --> helps support early pregnancy

Question 33

When do ecups regress?

Answer 33

120-150 days of gestation *If pregnancy loss after day 35 of gestation, cups will remain present and produce eCG --> mare will "lose a season" and not cycle back

Question 34

When do male and female fetal gonads undergo dramatic enlargement? and regression?

Answer 34

between 3 and 8 months of gestation enlargement causes excess androgen/estrogen levels in maternal blood --> behavioral (stallion) changes

Question 35

Equine twins - abortion rate? cause? complications? management options?

Answer 35

Abortion rate is HIGH! cause of abortion = placental insufficiency Complications: retained placenta, dystocia, ruptured prepubic tendon, rebreeding problems Management options: - let mare try to carry both to term --> bad - abort both embryos and rebreed --> clients don't like this - eliminate one embryo or 'pregnancy reduction' --> most common

Question 36

What is pregnancy reduction?

Answer 36

Reduction = one embryonic vesicle is disrupted and the other can continue to develop - optimally day 14-16 --> embryos will be fixed in position (migrate throughout uterus prior to this time)

Question 37

What are some management keys in mares prone to twins?

Answer 37

* anticipation --> evaluate for multiple ovulations * US at 14 days * Accurate detection * Early intervention --> immediately on detection

Question 38

Are twins (equine) always in two distinct embryonic vesicles? (

Answer 38

Nope