Ex 3 - Physiology of Pregnancy Flashcards
What is embryonic loss? and what is the incidence?
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
What happens if embryo is lost prior to MRP?
CL regresses at normal time; no delay in return to estrus –> continues to cycle
What happens if embryo is lost after MRP?
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
When do pig embryos enter the uterus?
at ~48 hrs
MRP in pigs
embryos migrate throughout uterus beginning on day 8-9 and spread apart –> cross-horn migration occurs –> migration stops at day 12
How many embryos are req’d for MRP to occur in PIGS?
at least 4 and at least 1 embryo must be in each uterine horn
What are some causes of early pregnancy loss?
maternal age, endometrial/uterine dz, P4 insufficiency, chromosomal abnormalities
others: nutrition, stress, early postpartum pregnancies
What is the placental membrane composed of?
maternal and embryonic/fetal components
What is the fetal membrane composed of?
only the fetal component
How does embryo get nutrients in early pregnancy?
secretions from endometrial glands –> micronutrients –> taken up by trophoblast cells, and eventually by the vascularized yolk sac
“Histotrophic support”
How does embryo get nutrients in later pregnancy?
Development of close assoc’d b/w maternal and fetal membranes
“Hemotrophic support”
What is implantation/attachment? and when does it occur?
- pigs
- sheep
- cows
- horses
An interdigitation of placental tissue with endometrium
- 14-18 days
- 15-18 days
- 18-22 days
- 35-38 days
what is the amnion and when does it develop?
membrane directly around fetus; 21 days
What is chorioallantois?
outer placental membrane
what is blastocoele cavity?
yolk sac –> storage of nutrients for embryonic development
What will make up the umbilical cord?
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
When can you start to see a fetal heartbeat?
day 25
What are the four types of placentas?
- diffuse
- cotyledonary
- zonary
- discoid
Diffuse placenta
*horse and pig
- microcotyledons evenly spread out across the entire placenta
- histotrophic and hemotrophic support occur throughout gestation
Cotyledonary placenta
- ruminants
- discrete attachment sites b/w cotyledons (placenta) and caruncles (uterus) –> form placentomes
Zonary placenta
- cats and dogs (carnivores)
- contact b/w placenta and endometrium in a band around the fetus
Discoid placenta
*primates
3 classifications of placentations
- Epitheliochorial
- Endothelliochorlal
- Hemochorial
Epitheliochorial
- 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!
Endotheliochorial
*Cats and dogs (carnivores)
- 4 layers of separation b/w mom and baby
- some transplacental transfer of Igs
**Colostrum is still very important
Hemochorial
*Primates and rodents
- 3 layers of separation
- fetal chorion comes into direct contact with maternal blood
**significant transplacental transfer of Igs
What are the two sources of P4?
CL and placenta
Which spp are CL-dependent for P4?
dogs, cats, goats, camelids
Which spp utilize both CL and placenta for P4? and how long is the CL needed?
Horse - 70 days
Sheep - 50 days
Cows - 6-8mo
What are equine endometrial cups?
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
What do e-cups produce and secrete?
eCG!!
may provide protection from the maternal immune system
eCG has both FSH and LH biologic activity
FSH in pregnant mares and ecups
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
When do ecups regress?
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
When do male and female fetal gonads undergo dramatic enlargement? and regression?
between 3 and 8 months of gestation
enlargement causes excess androgen/estrogen levels in maternal blood –> behavioral (stallion) changes
Equine twins - abortion rate? cause? complications? management options?
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
What is pregnancy reduction?
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)
What are some management keys in mares prone to twins?
- anticipation –> evaluate for multiple ovulations
- US at 14 days
- Accurate detection
- Early intervention –> immediately on detection
Are twins (equine) always in two distinct embryonic vesicles? (
Nope
