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ANIMAL PRODUCTION - Reproduction > 13 – Placenta > Flashcards

13 – Placenta Flashcards

1
Q

Placenta comprised of fetal and maternal tissue

A
  • Chorioallantoic
  • Choriovitelline (short lived in domestic species, ex. horses)
  • Endometrium
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2
Q

What are the major functional units of the placenta?

A
  • Chorionic villi
    o Projections on the surface of the chorion that closely interact with maternal tissue
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3
Q

Individual cells of chorionic villi=

A
  • Trophoblast
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4
Q

Due to differences in placental shape, structure and invasiveness large differences in

A
  • Endocrinological and
  • Immunological and
  • Metabolic communication between mother and fetus
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5
Q

Placental transport types

A
  • Diffusion
  • Facilitated diffusion
  • Active transport
  • Receptor-mediated endocytosis
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6
Q

Diffusion in placenta

A
  • Gases (ex. O2)
  • Simple molecules (drugs)
  • Water
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7
Q

Facilitated diffusion in placenta

A
  • Glucose
  • *carrier system operates with a chemical gradient
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8
Q

Active transport

A
  • AA
  • Water soluble vitamins
  • Na, K, Ca
  • *maintain higher concentrations in fetus than in mother
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9
Q

Receptor-mediate endocytosis

A
  • Immunoglobulins (IgG)
  • Protein
  • Fat
  • Viruses
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10
Q

Pig and horse placenta

A
  • Diffuse
  • Epitheliochorial
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11
Q

Diffuse placenta (pig and horse)

A
  • chorionic villi located over ENTIRE uterine luminal epithelium
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12
Q

Epitheliochorial placenta (pig and horse)

A
  • epithelium of chorionic villi and uterine luminal epithelium are intact
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13
Q

Porcine placenta

A
  • Allantois: mesenchyme and blood vessels
  • Chorionic epithelium: trophoblasts
  • Endometrium: epithelium and stroma (with uterine glands)
  • vessels are very close
  • uterine gland empty into AREOLA and taken up by chorion (fetal component)
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14
Q

Hemotrophic nutrition

A
  • Movement of substances from maternal to fetal circulations via crossing of intervening layers of cells
  • Ex. active transport, facilitated diffusion
  • *all placentae can achieve this
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15
Q

Histotrophic nutrition

A
  • Uptake of uterine gland secretions, tissue debris and maternal blood cells via PINOCYTOSIS or ENDOCYTOSIS
  • Occurs in varied placentae but especially in EPITHELIOCHORIAL
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16
Q

Areolae as sites of histotrophic nutrition

A
  • Top is columnar trophoblast capable of:
    o ENDOCYTOSIS and PINOCYTOSIS
    o Breakdown of absorbed material for transfer to fetal capillaries
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17
Q

Examples of nutrients that are taken up in histotrophic nutrition

A
  • Proteins
  • Uteroferrin: bi-iron protein (acid phosphatase
  • Vitamins(ex. placental folate)
  • Minerals
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18
Q

In between microcotyledons of the mare there are

A
  • Areolae
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19
Q

Chorionic girdle

A
  • First attachment of chorionic epithelium to the uterine epithelium PRIOR to the development of the microcotyledons
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20
Q

Endometrial cups in mare

A
  • Derived from a narrow band of thick trophoblast that develop around fetus (chorionic girdle)
  • Chorionic girdle peels off fetal membranes and trophoblast at d40 and INVADE to form the cups and produce eCG
  • Begin to be destroyed at d70 due to maternal immune attack
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21
Q

Equine chorionic gonadotropin (eCG) provides stimulus for

A
  • Maintenance of primary CL in the ovary formed from primary follicle
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22
Q

Gonadotrophins are typically produced in

A
  • Pituitary
  • *Horses are one species that produces gonadotrophins OUTSIDE of the pituitary (also humans)
23
Q

eCG stimulates formation and maintenance of

A
  • Accessory CL that produce more progesterone during pregnancy
24
Q

eCG levels

A
  • Detected in mare blood at 38-42 days post ovulation
  • Max levels at 60-70 days
  • No detection by 150 days
25
Q

eCG has FSH (except in mare) and LH-like activity

A
  • Provides signal for formation of accessory CLs (~40-60days gestation)
  • Regulates luteal steroidogenesis
26
Q

eCGs and accessory CLs

A
  • 40% via ovulation
  • 60% via luteinization of anovulatory follicles
27
Q

eCG stimulation of primary and accessory CLs

A
  • Increased circulating progesterone and plateaus (50-140days) then decrease
  • Low concentrations (180-200days)
  • Rapidly increase (300days) for parturition
28
Q

Cow, sheep and goat placenta

A
  • Cotyledonary
  • Syn-epitheliochorial
29
Q

Cotyledonary placenta (cow, sheep, goat)

A
  • Chorionic vascularized villous trophoblasts and uterine endometrial structures (CARUNCLES) come together
  • **placentomes
30
Q

Syn-epitheliochorial

A
  • Some trophoblast cells fuse together into binucleate giant trophoblast cells (BNGC)
    o BNGC migrate into uterine epithelium=fuse with maternal cells into trinucleate giant trophoblast
31
Q

Importance of multinuclear trophoblast secretions (BNGCs)

A
  • Important producers of progesterone, estradiol and placental lactogen
32
Q

Pregnancy-associated glycoprotines (PAGs) also referred to as

A
  • Pregnancy specific protein B (PSP-Bs)
33
Q

PAGs are a group of

A
  • Aspartic proteinases=enzymes that cleave proteins at aspartic residues
34
Q

Functions of PAGs (unclear)

A
  • Process or cleave growth factors and other maternally released factors at trophoblast-uterine interface
35
Q

Dog and cat placenta

A
  • Zonary
  • Endotheliochorial
36
Q

Zonary (dog and cat placenta)

A
  • Invasive band of chorion surrounds middle of fetus
37
Q

Endotheliochorial (dog and cat placenta)

A
  • Trophoblasts move through uterine epithelium and stroma
  • *in contact with maternal endothelia
  • *one layer is absent (endometrial layer has been ‘eroded’)
38
Q

Rat, mice and higher primates placenta

A
  • Discoid
  • Hemochorial
39
Q

Discoid placenta (rats, mice, higher primates)

A
  • Disc-like structure of chorion interacting with maternal tissue
40
Q

Hemochorial placenta (rats, mice, higher primates)

A
  • Highly invasive trophoblast pass through the maternal uterine epithelium, stroma, and endothelium of maternal vasculature becomes DIRECTLY in contact with maternal blood
  • *only 3 layers (maternal layers have been eroded)
41
Q

Which species can pass on passive immunity through the placenta?

A
  • Primates
  • Rodents
  • Dogs
  • Cats
  • **only IgG is transferred via receptor-mediated endocytosis as Fc receptors on trophoblast bind Fc portion of IgG
42
Q

Which species can NOT take up IgG

A
  • Horses
  • Pigs
  • Ruminants
  • *due to their extra layers in the maternal-fetal interface
43
Q

Placentate of all domestic species can produce steroids such as:

A
  • Estrogens
  • Progesterone (indispensable for pregnancy)
  • *except in dog
44
Q

Species with predominantly luteal P4 synthesis

A
  • Goat
  • Pig
  • *ONLY way in the dog (can’t produce from placenta)
45
Q

Placental steroidogenesis

A
  1. Cholesterol to pregnenotlone by P450scc
  2. Pregnenolone to progesterone by 3beta-HSD (Delta4 pathway: progestogens)
  3. Pregnenolone to dehydropiandrosterone to androstenedione
  4. Androstenedione to oestrone by P450arom then to oestradiol (Delta 5 pathway: androgens, estrogens)
46
Q

What organelle is able to do steroidogenesis?

A
  • Mitochondria
47
Q

Placental Steroidogenesis: cow and ewe

A
  • take cholesterol and mitochondria breaks it down into progesterone or estrogens
  • **IMPORTANCE of the multinucleated cells in the placentae of the ruminants
48
Q

Different estrogens produced by placenta (especially during last part of pregnancy in ungulates)

A
  • Estradiol
  • Estrone: major estrogen in ungulates
  • Equine specific forms: equilin and equilenin
49
Q

Mares and steroid production

A
  • can NOT make steroids from scratch
  • **NEED precursors from fetal gonads (ex. dehydroepiandrosterone)
50
Q

Relaxin

A
  • Small polypeptide hormone of the insulin superfamily
  • Produced by a number of tissues with a range of chemical effects between species
  • Acts via GPCRs
  • Not discovered in ruminants yet
51
Q

Relaxin in mares

A
  • Main secretion by placenta
52
Q

Relaxin in humans, cats, dogs

A
  • Placental AND trophoblast production
53
Q

Relaxin in pigs

A
  • Potent production by CL
  • *NOT produced by placenta

ANIMAL PRODUCTION - Reproduction (17 decks)

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