Pregnancy & Parturition

Question 1

Describe the difference between maternal recognition & implantation.

Answer 1

-maternal recognition = blocks luteolysis 12-16d
-implantation = placentation occurs - blastocyst hatches & embryo attaches to the wall of the uterus (endometrium) 15-20d *longer in mares due to capsule

Question 2

Describe the extraembryonic membranes of the placenta & its functions.

Answer 2

Extraembryonic membranes:
1. Trophoblast (chorion) - external placenta
2. Mesoderm (umbilical cord, allantois)
3. Ectoderm (amnion)

Functions:
-protection, nutrition, respiration, excretion, hormone production

Question 3

Describe the fetal membrane layers.

Answer 3

*yolk sac = nutrition & sex diff
1. Amnion = fluid, imp for mechanic protection, hydration, temp, movement
2. Umbilical cord = nutrition of embryo & secretion
3. Allantois = collect secretion from embryo & gas exchange
4. Chorion = outermost layer of placenta that attaches to uterus - nutrition of the embryo

Question 4

Describe the placental development.

Answer 4

1. Pre implantation
   -embryonic cells diff in ICM & trophoblast
2. Implantation
   -blastocyst hatches & loses ZP
   -trophoblast cells invade endometrium
3. Post implantation
   -circulation
4. End of pregnancy
   -reduced exchange between maternal & fetal circulation = parturition & placental delivery

Question 5

Describe the fetal & maternal components of the placenta.

Answer 5

1. Fetal = chorion
   -fetal blood capillaries
   -fetal CT
   -fetal chorionic epi
2. Maternal = endometrium
   -maternal blood capillaries
   -uterine CT
   -uterine epi

Question 6

Describe the classification of placentation. (4)

Answer 6

1. Source of vascular supply
2. Contact/intimacy of attachment
3. Distribution of villi to endometrium
4. Degree of involvement of fetal & maternal tissues

Question 7

Describe the source of vascular supply.

Answer 7

1. Chorio-vitelline
   -yolk fuses with chorion
   -yolk develops & allantois regresses
   -kangaroo
2. Chorio-allantoic
   -allantois fuses with chorion
   -yolk regress & allantois develops
   -mammals

Question 8

Describe the intimacy of attachment. (3)

Answer 8

1. Adeciduate
   -implantation is superficial = NO BLEEDING
   -pig, horse, cattle
2. Deciduous
   -intimate implantation
   -no uterine epi
   -man, rabbit, dog, cat
   -BLEEDING
3. Contra-deciduate
   -implantation intimate
   -PLACENTA NOT DELIVERED
   -moles

Question 9

Describe the distribution of villi.

Answer 9

1. Diffused
   -villi scattered on the surface of the chorion
   -mare, pig
2. Cotyledonary
   -villi in isolated patches
   -ruminants
3. Zonary
   -villi in a band encircling blastocyst/chorion sac
   -carnivores
4. Discoidal
   -villi in one or two discoidal areas
   -mouse, rat, rabbit, monkey, people

Question 10

Describe the degree of involvement of fetal & maternal tissues.

Answer 10

1. Epitheliochorial
   -intact membrane
   -trophoblast/chorionic & uterine epi close contact
   -horse, pig, marsupial, camelids
2. Syndesmochorial
   -fetal/maternal syncytium
   -uterine epi destroyed & chorionic villi contacts CT of uterine wall
   -ruminants
3. Endothelio-chorial
   -uterine epi & CT destroyed so chorionic villi contacts endothelium of maternal blood
   -dog & cat
4. Hemo-chorial
   -uterine epi, CT, endothelium destroyed & chorionic villi bath in maternal blood
   -human, mouse
5. Hemo-endothelial
   -fetal capillary lie in maternal blood
   -rabbit

Question 11

Describe placentation in bovine, equine, & canine.

Answer 11

1. Bovine
   -cotyledonary
   -chorioallantoic *
   -epitheliochorial
   -syndesmochorial
   -adeciduate
2. Equine
   -diffuse
   -chorioallantoic *
   -epitheliochorial
   -villous
   -adeciduate
3. Canine
   -zonary
   -chorioallantoic *
   -endotheliochorial
   -deciduate

Question 12

Describe the hormones of the placenta.

Answer 12

1. P2 = preg
2. E2 = develop placenta & baby organs
3. Relaxin = body prepares for delivery by loosening muscles & ligaments of pelvis
4. Placental lactogen = regulate metabolism, glucose, amino acid, lipid metabolism in mom, mobilize nutrients for transport to fetus
5. Chorionic gonadotrophins (primates) = luteotrophic hormone for maternal recog of preg
6. Prolactin = breast tissue/milk
7. ECG = made by endometrial cups to make secondary/accessory CL

Question 13

Describe endometrial cups.

Answer 13

-allantoic pouch
-migrate chorionic girdle into maternal endometrium
-day 35
-make eCG
>detectable day 35
>peak day 60
>gone day 100-150 (disappear due to embryo & moms immune system)
*eCG similar to LH & FSH

Question 14

Describe fetal-placental progestin in horse, cattle, dog.

Answer 14

1. Horse
   -similar to P4
   -appear day 40
   -increase until day 300
2. Cattle
   -CL major source of P4
   -placenta makes estrogens
3. Dog
   -ovaries make P4

Question 15

Describe the role of P4 in pregnancy.

Answer 15

1. Placental development & function
2. Myometrial quiescence
3. Cervical closure
4. Immune mediation

Question 16

Describe fetal placental estrogens.

Answer 16

-fetal gonads make androgens -> androgen aromatized to estrogen in placenta
*equine specific

Question 17

Describe relaxin in cow VS mare.

Answer 17

Mares
-made by CL & placenta
Cow
-made only by CL

Question 18

Describe the physiology of parturition.

Answer 18

-activation of fetal hypothalamic-pitutary-adrenal axis
>increase oxytocin & PGF
>fetal hypoxemia & size
-CRH -> ACTH -> cortisol
-fetal maturation (lung, kidney, brain) = high cortisol
-switch in P4:E2 ratio
-prostaglandin/oxytocin by placenta/uterus
-relaxin/estrogen soften ligaments & cervical ripening

Question 19

Describe the phases of parturition.

Answer 19

1. Relax pelvic lig, dilation of cervix, vag, vulva
   -fergusson reflex = pressure on cervix by fetus
2. Expulsion of fetus
3. Fetal membrane delivery

Question 20

Describe the transition from intrauterine to extrauterine.

Answer 20

1. Respiration = lung adaptation
   -clear lung fluid, surfactant secretion, consistent breaths
2. Circulatory = removal of low pressure placenta
   -CVS response via change in blood flow, pressure & pulmonary vasodilation
3. Thermoregulation & energy metabolism control