Types of Placenta

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Types of Placenta
Diffuse Placenta
Discoid Placenta
Chorionic Plate
Mare
Sow
Cotyledonary Placenta
Human
Cow
Ewe
Also Goat Deer
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Placentome in Ruminants
Cow
Ewe
Chorion
Chorion
Caruncle
Caruncle
Endometrium
Endometrium
Mare, Sow
Chorion
Microcotyledon
Endometrium
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Placental Attachment in Ruminants
Carry Placental Lactogen into maternal blood
Chorion
Binucleate Cell
Migrate and fuse with uterine epithelium
Uterine Epithelium
Syncytium
Capillary
Fusion of Binucleate cells and uterine epithelium
(multinucleate)
Stroma
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Binucleate Cell Migration into the Uterine
Epithelium
Fusion of B.C. with Uterine Epithelium
Binucleate Cell
Syncytium
Chorion
Uterine Epithelium
Stroma
Photomicrograph provided by Gordon J. King
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Placental Lactogens (Protein Hormones)
Prolactin-like activity
Stimulates Milk Synthesis
Not Present in Pig and Mare
May regulate maternal metabolism to facilitate
fetal growth High levels in the last 1/3 of
gestation. High levels facilitate higher milk
production. Dairy cows have higher blood
concentrations than beef cows
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Placentomes in Ruminants
Attachment of placental cotyledons to
caruncle forms placentome
Maternal vascularity supplies the needed
nutrients for fetal development
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Placental-Uterine Attachment
Microcotyledon (Fetal)
Umbilical Vessels
Allantois
Increase placental surface area
Chorion
Endometrial Epithelium
Micro- cotyledon (Maternal)
Micro- cotyledon
Endometrial Glands
Uterine Arteries
Uterine Veins
Redrawn with permission Steven, D.H. Samuel,
C.A.. 1975. J. Reprod. Fertil. 23579
Endometrium
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Fetal Nutrition (Farm
Animals) Blood gas exchange at chorion -
endometrium attachment. Placenta highly
permeable to water and electrolytes i.e., stored
in and exchange between allantoic and amniotic
fluids. Placenta converts glucose to fructose.
Fetal fat formed from fatty acids transferred
across the placenta. Fetus makes proteins from
transferred amino acids. Water soluble
vitamins cross the placenta easier than fat
soluble. Minerals are transferred across the
placenta. Antibodies to fight disease do not
cross the placenta - the newborn will get
these antibodies from the first milk - Colostrum.
Allows storage in allantoic fluid
In Domestic Species
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Hormonal Control of
Gestation Progesterone - Main Hormone
-Causes uterine quiescence and
histotroph production Sources of
Progesterone During Gestation

Gestation Sheep - CL to
day 50 then placenta 148 days
Cow - CL throughout. However, after
280 days day 215
placenta and adrenal produce
enough progesterone to
maintain pregnancy
Sow - All
from CL
114 days
Can remove CL after day 50 and not cause abortion
Remove CL at any time causes abortion
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Gestation
1st CL produces progesterone up to 180 days,
FSH stimulates follicles growth and eCG (PMSG)
causes CL's to form from follicles. They
secrete progesterone and are active from day
40-180. Progesterone is low until 270 days -
rises in last 5 months due probably to
placental progesterone production.
Mare -
337 days
PMSG - Pregnant Mare Serum Gonadotropin Now call
eCG Origin is Endometrial cups
Endometrial cups form from invasion of the
chorionic girdle cells surround the spherical
placenta of mare. These invade into the uterine
endometrium on Days 30 to 35 of gestation to form
the ulcer-like cups.
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Placental Development in the Mare
Day 25
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Placental Development in the Mare
Day 40
Day 34
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Chorionic Girdle
Chorioallantois
Yolk Sac
Embryo
Reproduced with permsission of Dr. O. J. Ginther,
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Endometrial Cups
Accessory CLs
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Hormone Patterns During Mare Gestation
Declines in Mare
eCG may be involved with immunoprotection of fetus
Invasion of chorionic girdle cell
Accessory CL form by ovulation and luteinization
Reproduced with permission Ginther,
O.J. Reproductive Biology of the Mare
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Mare can have problems with twins Must get rid
of one before Day 30 or if both are lost
after Day 30 endometrial cups will have
formed! Cannot rebreed until another 60 to 90
Days when cups are shed. Similar problem with a
mare which aborts after Day 30 Mare which have
problems with blood progesterone during early
pregnancy can be given Regumate or injected with
progesterone Colic can cause problems if PGF2a
gets elevated and causes CL regression