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Animal Production > Placenta > Flashcards

Placenta Flashcards

1
Q

Placenta

A

-composed of fetal and maternal tissues
>Chorion and allantois (Chorioallantoic- major in eutherians)
>Chorion and yolk sac (choriovitelline- most domestic animals)
>Endometrium/Decidua

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2
Q

Chorionic villi

A

-Major functional units

-projections on the surface of the chorion that closely interact with maternal tissues

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3
Q

What are the individual cells of the villi?

A

trophoblast

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4
Q

Where do differences occur between placentas?

A

-endocrinological
-immunological
-metabolic communication between mother and fetus

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5
Q

Function of placenta during pregnancy

A

-transfer O2, CO2
-fetal nutrition
-excretory fucntions (water balance, pH regulation)
-hormone/enzyme production
-immunological functions

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6
Q

Placental transport

A

-Diffusion
-facilitated diffucion
-active transport
-receptor-mediated endocytosis

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7
Q

Diffusion in placenta

A

Gases, simple molecules, water movement

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8
Q

Facilitated diffusion in placenta

A

glucose moves with a chemical gradient

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9
Q

Active transport in placenta

A

-essential amino acids, water soluble vitamins, Na, K, Ca
**maintain higher concentrations in fetus than mother

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10
Q

Receptor-mediated endocytosis

A

-immunoglobulins (IgG), some protein, fat, viruses

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11
Q

Pig and Horse placenta

A

-Diffuse- chorionic villi located over the entire uterine luminal epithelium

-Epitheliochorial- epithelium of chorionic villi and uterine luminal epithelium are intact

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12
Q

Types of nutrition of placenta

A

-Hemotrophic

-Histotrophic

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13
Q

Hemotrophic nutrition

A

-movement of substances from maternal to fetal circulation via crossing of intervening layers of cells

Eg. active transport, facilitated diffusion

**All placenta types do this

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14
Q

Histotrophic nutrition

A

Uptake of uterine gland secretions, tissue debris, maternal blood cells via pinocytosis or endocytosis

-occurs in varied placentae but especially in epitheliochorial

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15
Q

Areolae

A

-Top: columnar trophoblast capable of endocytosis and pinocytosis and breakdown of absorbed materials for transfer to fetal capillaries

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16
Q

What nutrients are taken up by Areolae?

A

-proteins
-Uteroferrin (bi-iron protein)
-vitamins
-minerals

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17
Q

What form of nutrition is easily accomplished with areolae?

A

Histotrophic

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18
Q

Microcotyledons of mare

A

-both maternal and fetal circulation very close together
>use hemotrophic nutrition

-has smaller areolae linked with microcotyledons

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19
Q

Endometrial cups

A

-derived from a narrow band of thick trophoblast that develop around the fetus (chorionic girdle ~day 25)

-Day 40- girdle peels off fetal membranes and trophoblast invade the endometrium to form the cups and produce eCG

-Day 70- destroyed due to maternal immune attack

20
Q

Chorionic girdle attachment

A

The first attachment of the chorionic epithelium to the uterine epithelium prior to the development of the microcotyledons

21
Q

eCG (equine chorionic gonadotropin)

A

-A gonadotropin of placenta

-provides a stimulus for maintenance of the primary CL in the ovary formed from primary follicle AND stimulates formation and maintenance of accessory CL’s that produce more progesterone during pregnancy

22
Q

eCG levels throughout pregnancy

A

-Glycoprotein is detected around 38-42 days

-Max levels occur 60-70 days and then decline with little or no detection by 150 days of gestation (due to endometrial cups being attacked by maternal immune system)

23
Q

Accessory CL’s

A

Develop 40-60 days gestation from ovulation, and luteinization of anovulatory follicles

-Receives eCG signal (LH and FSH like activity)

24
Q

eCG function

A

-Provides signal for formation of the accessory CLs

-Regulates luteal steroidogenesis

25
Q

eCG stimulation of primary and accessory CLs

A

-increased circulating progesterone concentrations which plateau between 50-140 days of gestation then decrease

-from 180-200 days, concentrations will be very low until day 300 when progesterone rapidly increases again for parturition

26
Q

Cow, sheep, goat placenta

A

Cotyledonary and Syn-epitheliochorial

27
Q

Cotyledonary

A

-chorionic vascularized villous trophoblasts and uterine endometrial structures = caruncles come together= “spot weld”

Caruncles and cotyledons combine to be placentomes

28
Q

Syn-epitheliochorial

A

Some trophoblast cells fuse together into binucleate giant trophoblast cells (BNGC)

> BNGC migrate into the uterine epithelium where they can fuse with maternal cells into trinucleate giant trophoblast

29
Q

Pregnancy Associated glycoproteins

A

**also called pregnancy specific proteins B (PSP-Bs)

-large groups of aspartic proteinases (cleave proteins at aspartic residues)

-unclear function- likely process or cleave growth factors and other maternally released factors at trophoblast-uterine interface

30
Q

Dog and cat placenta

A

-zonary
-endotheliochorial

31
Q

Zonary

A

An invasive band of the chorion surrounds the middle of the fetus

32
Q

Endotheliochorial

A

-trophoblasts move through uterine epithelium, stroma, and are in contact with maternal endothelia

33
Q

Rats, mice, higher primates placenta

A

-discoid
-hemochorial

34
Q

Discoid

A

-a disk like structure of chorion interacting with maternal tissue

35
Q

Hemochorial

A

-highly invasive trophoblast pass through the maternal uterine epithelium, stroma, and endothelium of maternal vasculature becoming directly in contact with maternal blood

36
Q

Passive immunity transfer through placenta

A

-occurs in primates, rodents, dogs, cats
-due to slight (endotheliochorial) or considerable (hemochorial) trophoblast invasion with maternal blood

**only IgG is transferred via receptor mediated endocytosis because Fc receptor on trophoblasts

37
Q

IgG transfer in horses, pigs, ruminants

A

**does not occur due to extra layers in the maternal-fetal interface
-IgGs passed only via colostrum in there species

38
Q

Placenta secreting progesterone

A

-Placenta of all domestic species can produce steroids like estrogen and progesterone EXCEPT DOG

39
Q

Progesterone role in pregnancy

A

Progesterone NEEDED for pregnancy.
>Horse has 5alpha-dihydroprogesterone as potent progesterone
>mostly luteal progesterone synthesis (goat, pig, and only in dog)
>Bovine- an intermediate between luteal and placental production

40
Q

Placental steroidogenesis

A

Two pathways
1.Delta 4 pathway= progestogens

  1. Delta 5 pathway= androgens and estrogens
41
Q

Delta 4 pathway

A

Cholesterol -> Pregnenolone (and 3B-HSD) -> progesterone

42
Q

Delta 5 pathway

A

Dehydroepiandrosterone -> Androstenedione (and P450aromatase enzyme) -> Oestrone <-> Oestradiol

43
Q

Placental steroidogenesis in cow and ewe

A

Use both spatial and temporal compartmentalization

  1. Uninucleate Trophoblast cell (UTC)-use cholesterol to produce pregnenolone and Dehydroepiandrosterone
  2. Trophoblast Giant Cell (binucleate and trinucleate)- use products of UTC to make progesterone, androstenedione, and oestrone
44
Q

Estrogens

A

-important product of placenta

-many different types (estradiol, estrone, equine specific equilin and equilenin

45
Q

Mare estrogen formation by placenta

A

-Placenta cannot make steroids by scratch, needs precursors from fetal gonads

46
Q

Relaxin

A

A small polypeptide hormone of the insulin superfamily
-7 ID’d relaxin peptides; many GPC receptors
-produced by many different tissues

47
Q

Relaxin secretion

A

Mares: placenta

Humans, dogs, cats: trophoblasts

Pig: CL, not placenta

Ruminants: not discovered yet

Animal Production (17 decks)

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