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Blastulation
Gap Junctions
Lecture 19
Placentation and Maternal
Recognition of Pregnancy
Inner Cell Mass
Na+
Animal Science 434
John J. Parrish
Zona Pellucida
Trophectoderm
[Na+]
H2O
Tight Junctions
Hatching
Conceptus Growth
Occurs in cow, pig and sheep
 Bovine
Cow
• Day 15, 1-2 mm
• Day 18-19, 10-20 cm
» 9 - 11 days
Embryonic
Area
Spherical
 Equine, Ovine
» 7 - 8 days
 Porcine
» 6 days
Tubular
Elongating
Trophoblast
Mare
remains
spherical!
Filamentous
Development of Porcine Conceptuses
from Day 10 to 12
Elongated Day 15 Porcine
Conceptus
5 mm Spherical
10 mm Spherical
Inner Cell
Mass
15 mm Tubular
150 mm
Filamentous
Embryo
1
Uterine Location of Elongating
Ruminant Blastocyst
Pig Intrauterine Migration
Day 5
Corpus
Luteum
Bovine and
Ovine
Pig Intrauterine Migration
Pig Intrauterine Migration
Day 7
Day 12
Embryos
become fixed
Trans-uterine Migration in the Mare
Begins Day 10
Fixation can
occur in either
horn!
Fixation
on day
15 - 16
Gastrulation
Trophectoderm
Inner Cell Mass
Formation
of Germ
Layers
Corpus
Luteum
Transuterine
migration is rare
in cow and ewe!
Endoderm
Blastocoele
Cavity
2
Gastrulation
Gastrulation
Endoderm
Endoderm
Yolk Sack
Yolk Sack
Gastrula
Gastrula
Ectoderm
Trophectoderm
Ectoderm
Extraembryonic
Coelom
Mesoderm
Yolk Sack
Endoderm
Trophectoderm
(Chorion)
Endoderm
Germ Layers
 Ectoderm
» CNS
» Sense organs
» Mammary
glands
» Sweat glands
» Skin
» Hair
» hooves
 Mesoderm
» Circulatory
» Skeletal
» Muscle
» Reproductive
tracts
» Kidneys
» Urinary ducts
 Endoderm
Embryonic
Ectoderm
Placenta Formation
» Digestive
» Liver
» Lungs
» Pancreas
» Thyroid gland
» Other glands
Amniotic Folds
Extraembryonic
Ceolom
Yolk
Sack
Trophectoderm
Mesoderm
Chorion
Endoderm
3
Amniotic Fold
Amnionic Cavity
Amniotic Cavity
Amnion
Uterine
Lumen
Allantois
Yolk
Sack
Extraembryonic
Ceolom
Allantois
Yolk
Sack
Chorion
Chorion
Chorion
Extraembryonic
Ceolom
Carnuncle
Placental Membranes
Amniotic Cavity
Amnion
 Yolk Sack
» In birds to nourish embryo
» In mammal atrophies but source of blood
cells and primordial germ cells
 Amnion
» Non-vascular, fluid filled
» Fluid produced by fetus
» Protective cushion
» Ruptures at birth (not breaking of water)
Allantois Cavity
Yolk
Sack
Allantochorion
(Chorioallantois)
Cotyledon
Placental Membranes (cont.)
 Allantois
» Blood vessels
» Fuses with chorion
• Allantochorion or chorioallantois
• Brings blood vessels to chorion
Maternal Recognition of Pregnancy
 Chorion
» Outermost membrane
» Attachment to mother
4
Luteal Regression
CL Status
CA
(+)
Uterine PGF2α
CL
PGF2α
(Bovine, Ovine,
Porcine)
PGF2α
(Equine)
Conceptus Secretions
• Proteins
• Steroids
Recognition of Pregnancy in the Porcine
CL Regression
•Luteolytic
•No CL support
CL Maintenance
•Antiluteolytic
» Block PGF2α effects
Filamentous Embryo
(+)
No Uterine Factor
(human)
Recognition of Pregnancy
Mechanisms
•Luteotrophic
» Stimulate progesterone
production by CL
Maintained
Recognition of Pregnancy in Bovine
and Ovine
Conceptus Secretions
• Interferons
•oIFN-τ
•bIFN-τ
Mechanism
• Antiluteolytic
• Inhibit oxytocin
receptor synthesis
• Inhibit PGF2α
synthesis
Critical Days
• Bovine - 16 to 17
• Ovine - 12 to 13
Recognition of Pregnancy in the Porcine
E2
E2
E2
PGF2α
PGF2α
PGF2α
PGF2α
E2
E2
E2
PGF2α
PGF2α
5
Recognition of Pregnancy in the Porcine
Recognition of Pregnancy in the Mare
Conceptus Secretions
• Estradiol
E2
E2
Critical Days
PGF2α
E2
PGF2α
11 to 12
PGF2α
E2
E2
PGF2α
E2
Mechanism
PGF2α
•Antiluteolytic
»Redirect PGF2α
»Requires 2 embryos per horn
Recognition of Pregnancy in the Human
PGF2α
Conceptus Secretion
• ?
Mechanism
• antiluteolytic
Critical Days
10 to 14
Recognition of Pregnancy
Conceptus Secretes
• HCG
Mechanism
• luteotrophic
INF-τ
HCG
Critical Days
•8 to 12
Conceptus Secretions
• Proteins
• Steroids
HCG
Estradiol
Dog and Cat
 CL does not regress if not pregnant
» no uterine effect
 Psuedopregnancy
» CL last similar length as in pregnancy
Implantation
6
Time of Implantation
Type of Implantation
Attachment to Uterus
Species
Beginning
 Superficial
» Chorion lies opposed to uterine wall
» Farm animals
Completion
pig
13
24
cow
22
40
sheep
15
28
mare
24 - 40
95 - 100
human
7-8
30
 Eccentric
» Chorionic sack in a uterine fold
» Rodent
 Interstitial
» Embryo digests part of uterine wall
» human
Degree of Tissue Loss at Parturition
 Deciduate
Shape or Distribution of Chorionic Villi
 Cotelydonary - cow, sheep
» Eccentric, interstitial
» Rodent, human
 Diffuse - pig, horse
 Zonary - dog, cat
 Indeciduate or Nondeciduate
 Discoid - human
» Superficial
» Farm animals
Cotelydonary
Placenta
Cotelydonary
Placenta
Cow
Cow
Convex
Cotelydon (Chorion)
Ewe
Concave
Placentome
Ewe
Caruncle
70 - 120
90 - 100
Endometrium
7
Day 23 Migration of Bicnucleate Cells and
Formation of Syncytium
Placental Attachment in Ruminant
Binucleate
Cell
Chorion
Migrate and
fuse with
uterine
epithelium
Uterine
Epithelium
Binucleate
Cell
Syncytium
Capillary
Fusion of
Binucleate
cells and
uterine
epithelium
Stroma
Endometrial
Stroma
Multinucleated Cells in
Uterine Epithelium
(multinucleate)
Binuclear Giant Cells
Placental Lactogens (Protein Hormones)
Prolactin-like activity: Stimulates Milk Synthesis
 20% of fetal placenta
Not Present in Pig and Mare
 Invade endometrium
 Source
» Placental lactogen
» Pregnancy specific protein B
• 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
Pregnancy Specific Protein B
Diffuse Placenta
Horse
 Unique to ruminants
 Function uncertain
Pig
 Has been used to detect pregnancy
» Cattle, sheep, deer
• Can be used to detect pregnancy in cows after
day 25
»Not early pregnancy factor!!!
Microcotyledons
8
Microcotelydons
Endometrial Cups in Mare
Increase placental
surface area
 From both trophoblast and endometrium
Microcotelydon
(Fetal)
Microcotelydon
Epithelium
 5 to 10
 Form between days 35 to 60
Endometrium
Microcotelydon
(Maternal)
Endometrial
Glands
Uterine
Arteries
 Produce equine chorionic gonadotropin
(eCG, PMSG)
 Sloughed off after day 60
Uterine Veins
Zonary Placenta
(bitch, queen)
Discoid Placenta
(human)
Cell Layers Separating Maternal and Fetal Blood
Histological Classification
Fetal
Maternal
Tissues
Capillary
Endothelium
Connective
Tissue
Chorionic
Epithelium
syndesmochorial
endothelialchorial
hemochorial
hemoendothelial
Maternal
endothelium +
conn. tissue +
epithelium
+
+
+
-
+
-
-
-
Fetal
epithelium
+
conn. tissue +
endothelium +
+
+
+
+
+
+
+
+
+
+
*ruminant
dog
cat
human
rat
rabbit
Capillary
Endothelium
Connective
Tissue
Endometrial
Epithelium
Species
epithelialchorial
pig
horse
ruminant
9
Important!!!!
 In all cases, fetal and maternal blood
does not mix.
10