Placentation, Gestation, Parturition

Question 1

Placenta

Answer 1

Organ of physiologic exchange

• fusion of fetal membranes to endometrium
• size/functions change with pregnancy stages
• expelled after parturition (stage 3)

Question 2

Placenta is classified based on

Answer 2

Gross shape and distribution of villi

- microscopic structure of feto-maternal barrier

Question 3

Villi function

Answer 3

Bring fetal vessels into close proximity to maternal blood vessels

Question 4

Diffuse

Answer 4

Attached everywhere

- mare and sow

Question 5

Cotyledonary

Answer 5

Attachment occurs in small, multiple focal areas

- ewe, doe, cow

Question 6

Zonary

Answer 6

Attachment occurs in a specific circular zone around the fetus
- bitch and queen

Question 7

Discoid

Answer 7

Attachment occurs in one large single area (large cotyledon)

- primates and rodents

Question 8

Convex villi

Answer 8

Cow, giraffe

Question 9

Concave villi

Answer 9

Sheep, goat

Question 10

Fetal _____ fuse with maternal ______ to form ______

Answer 10

Cotyledons; caruncles; placentomes

Question 11

Maternal caruncles

Answer 11

Specialized projections of uterine mucosa

- convex in cow, concave in ewe/doe

Question 12

Functional unit

Answer 12

Placentome

Question 13

Utero verdin

Answer 13

Dark green fluid

Question 14

Binucleate giant cells

Answer 14

Move from fetal side across junction, into maternal side to secrete substances (pregnancy specific protein B) that are used to detect pregnancy
- basis for pregnancy blood test

Question 15

Epitheliochorial

Answer 15

Least intimate, both maternal and fetal epithelium are intact

• greatest barrier
• pig, horse, cow, ewe, doe

Question 16

Endotheliochorial

Answer 16

Complete erosion of endometrial epithelium

- dog, cat

Question 17

Hemochorial

Answer 17

Chorionic epithelium is in direct apposition to maternal pools of blood

• intimate, close attachment
• primates, rodents

Question 18

Degree of invasiveness is important for transfer of _____

Answer 18

Maternal antibodies

- need to colostrum is high in pigs, cows, ewes

Question 19

Deciduate

Answer 19

Portion of endothelium is shed with placenta

- dog, cat, rodents, primate

Question 20

Adeciduate

Answer 20

Endometrium is left intact at time of placenta expulsion

- pig, cow, horse, sheep, goat

Question 21

Placental functions

Answer 21

• metabolic exchange

- substitutes for fetal GIT, lung, kidney, liver, endocrine glands

Question 22

The placenta produces hormones that _____

Answer 22

• stimulate ovarian functions
• maintain pregnancy
• stimulate mammary function
• assist in delivery of fetus

Question 23

In which species does the placenta NOT have a role in pregnancy maintenance?

Answer 23

• bitch
• queen
• camels
• sow
• doe

Question 24

The placenta takes over from primary (ovarian) source of progesterone in _______

Answer 24

Cow, ewe, and mare

• cow: 6-8 mos
• ewe: 50 days
• mare: 70 days

Question 25

Endometrial cups are unique to the _____

Answer 25

Mare - produce equine chorionic gonadotropin - temporary structure - embed and invade maternal endometrium - could measure eCG level to determine pregnancy (is highest around 80 days)

Question 26

Placental circulation

Answer 26

2 circulations parallel to each other - blood does not intermingle between dam and fetus - close enough for gas and nutrient exchange to occur

Question 27

Freemartinism

Answer 27

Blood can be co-mingled between twins of cattle but rarely of other species - anastomosis of fetal circulation - mascinulizes female = sterility

Question 28

What species has the most variable gestation length?

Answer 28

Mare | - 340-360 days

Question 29

Placental takeover of P4 production in the cow and mare

Answer 29

150 days

Question 30

Gestation lengths

Answer 30

- cow: 283 days - ewe: 152 days - doe: approx 230 days - sow: 114 days - dog: 58-68 days - cat: 64-67 days - camelids: 11 months

Question 31

Amniotic fluid

Answer 31

- origin: fetal urine, secretions from respiratory and buccal cavity, maternal circulation - functions: protects fetus from external shock, prevents fetal skin adhesion to membrane, dilates cervix and lubricates birth passage

Question 32

Allantoic fluid

Answer 32

- origin: fetal urine, secretions of allantoic membrane - functions: brings allochorion into close apposition with endometrium, stores fetal excretory products not transferred to mother, maintains osmotic pressure of fetal plasma

Question 33

Fetal fluids

Answer 33

Function to protect and bathe the fetus - lubricate birth canal - elimination of waste - maintains osmotic pressure of fetal plasma, prevents fluid loss to maternal circulation

Question 34

Hippomanes

Answer 34

Allantoic calculi, similar to bladder stones - do not serve physiologic purpose - seen occasionally in cattle, common in equines

Question 35

Stage 1 of parturition

Answer 35

Initiation of myometrial contractions - P4 block has been removed via PGF - P4 converted to E2

Question 36

Stage 2

Answer 36

Expulsion of fetus | - strong myometrial and abdominal contractions expels fetus

Question 37

Stage 3

Answer 37

Expulsion of fetal membranes

Question 38

Active straining is due to

Answer 38

Abdominal contractions

Question 39

Fetal stress drives the ____

Answer 39

Parturition cascade

Question 40

Myometrial contractions

Answer 40

Uterus is transformed from P4 dominated "relaxed" state to an "active" state - PGF synthesis and release is increased - act jointly to initiate uterine contractions needed to dilate the cervix and deliver the fetus

Question 41

Immune stats

Answer 41

Fetus synthesizes little to no antibodies - acquires antibodies from dam while in utero (rat, human) - secretes antibodies in colostrum (farm animals) - related to impermeability of epitheliochorial placenta to antibodies