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Lecture 19 Placentation and Maternal Recognition of Pregnancy
Animal Science 434 John J. Parrish
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Blastulation Gap Junctions Inner Cell Mass Zona Pellucida
Trophectoderm Na+ [Na+] H2O Tight Junctions
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Hatching Bovine days Equine, Ovine 7 - 8 days Porcine 6 days
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Mare remains spherical!
Conceptus Growth Cow Day 15, 1-2 mm Day 18-19, cm Occurs in cow, pig and sheep Spherical Embryonic Area Tubular Elongating Trophoblast Mare remains spherical! Filamentous
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Development of Porcine Conceptuses from Day 10 to 12
5 mm Spherical 10 mm Spherical Inner Cell Mass 15 mm Tubular 150 mm Filamentous
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Elongated Day 15 Porcine Conceptus
Embryo
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Uterine Location of Elongating Ruminant Blastocyst
Corpus Luteum Bovine and Ovine
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Pig Intrauterine Migration
Day 5
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Pig Intrauterine Migration
Day 7
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Pig Intrauterine Migration
Day 12 Embryos become fixed Transuterine migration is rare in cow and ewe!
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Trans-uterine Migration in the Mare
Begins Day 10 Fixation can occur in either horn! Fixation on day Corpus Luteum
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Formation of Germ Layers
Gastrulation Trophectoderm Inner Cell Mass Formation of Germ Layers Endoderm Blastocoele Cavity
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Gastrulation Endoderm Endoderm Yolk Sack
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Gastrulation Endoderm Endoderm Yolk Sack
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Gastrula Ectoderm Trophectoderm Endoderm
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Trophectoderm (Chorion)
Gastrula Ectoderm Mesoderm Extraembryonic Coelom Yolk Sack Endoderm Trophectoderm (Chorion)
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Germ Layers Ectoderm Mesoderm Endoderm CNS Sense organs Mammary glands
Sweat glands Skin Hair hooves Mesoderm Circulatory Skeletal Muscle Reproductive tracts Kidneys Urinary ducts Endoderm Digestive Liver Lungs Pancreas Thyroid gland Other glands
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Extraembryonic Ceolom
Placenta Formation Embryonic Ectoderm Amniotic Folds Extraembryonic Ceolom Yolk Sack Trophectoderm Chorion Mesoderm Endoderm
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Extraembryonic Ceolom
Amniotic Fold Amniotic Cavity Allantois Extraembryonic Ceolom Yolk Sack Chorion
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Extraembryonic Ceolom
Amnionic Cavity Amnion Uterine Lumen Allantois Yolk Sack Chorion Extraembryonic Ceolom Carnuncle
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Amniotic Cavity Chorion Amnion Allantois Cavity Yolk Sack Allantochorion (Chorioallantois) Cotyledon
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Placental Membranes Yolk Sack Amnion 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)
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Placental Membranes (cont.)
Allantois Blood vessels Fuses with chorion Allantochorion or chorioallantois Brings blood vessels to chorion Chorion Outermost membrane Attachment to mother
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Maternal Recognition of Pregnancy
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Luteal Regression PGF2a (Bovine, Ovine, Porcine) PGF2a (Equine)
No Uterine Factor (human)
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CL Status CA Mechanisms CL Regression Luteolytic No CL support
CL Maintenance Antiluteolytic Block PGF2a effects Luteotrophic Stimulate progesterone production by CL (+) Uterine PGF2a CL Filamentous Embryo (+) Maintained
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Recognition of Pregnancy
Conceptus Secretions Proteins Steroids
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Recognition of Pregnancy in Bovine and Ovine
Conceptus Secretions Interferons oIFN-t bIFN-t Mechanism Antiluteolytic Inhibit oxytocin receptor synthesis Inhibit PGF2a synthesis Critical Days Bovine - 16 to 17 Ovine - 12 to 13
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Recognition of Pregnancy in the Porcine
PGF2a
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Recognition of Pregnancy in the Porcine
PGF2a PGF2a PGF2a
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Recognition of Pregnancy in the Porcine
Conceptus Secretions Estradiol PGF2a E2 Critical Days 11 to 12 Mechanism Antiluteolytic Redirect PGF2a Requires 2 embryos per horn
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Recognition of Pregnancy in the Mare
PGF2a Mechanism antiluteolytic Conceptus Secretion ? Critical Days 10 to 14
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Recognition of Pregnancy in the Human
Conceptus Secretes HCG Mechanism luteotrophic HCG Critical Days 8 to 12
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Recognition of Pregnancy
INF-t HCG Estradiol Conceptus Secretions Proteins Steroids
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Dog and Cat CL does not regress if not pregnant Psuedopregnancy
no uterine effect Psuedopregnancy CL last similar length as in pregnancy
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Implantation
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Time of Implantation Attachment to Uterus Species Beginning Completion
pig 13 24 cow 22 40 sheep 15 28 mare human
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Type of Implantation Superficial Eccentric Interstitial
Chorion lies opposed to uterine wall Farm animals Eccentric Chorionic sack in a uterine fold Rodent Interstitial Embryo digests part of uterine wall human
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Degree of Tissue Loss at Parturition
Deciduate Eccentric, interstitial Rodent, human Indeciduate or Nondeciduate Superficial Farm animals
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Shape or Distribution of Chorionic Villi
Cotelydonary - cow, sheep Diffuse - pig, horse Zonary - dog, cat Discoid - human
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Cotelydonary Placenta
Cow Convex Ewe Concave Cotelydon (Chorion) Caruncle Endometrium
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Cotelydonary Placenta
Cow Ewe Placentome
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Placental Attachment in Ruminant
Binucleate Cell Chorion Migrate and fuse with uterine epithelium Uterine Epithelium Syncytium Capillary Fusion of Binucleate cells and uterine epithelium (multinucleate) Stroma
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Day 23 Migration of Bicnucleate Cells and Formation of Syncytium
Binucleate Cell Endometrial Stroma Multinucleated Cells in Uterine Epithelium
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Binuclear Giant Cells 20% of fetal placenta Invade endometrium Source
Placental lactogen Pregnancy specific protein B
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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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Pregnancy Specific Protein B
Unique to ruminants Function uncertain Has been used to detect pregnancy Cattle, sheep, deer Can be used to detect pregnancy in cows after day 25 Not early pregnancy factor!!!
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Diffuse Placenta Horse Pig Microcotyledons
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Increase placental surface area Microcotelydon (Fetal)
Microcotelydons Increase placental surface area Microcotelydon (Fetal) Microcotelydon Epithelium Microcotelydon (Maternal) Endometrial Glands Endometrium Uterine Arteries Uterine Veins
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Endometrial Cups in Mare
From both trophoblast and endometrium 5 to 10 Form between days 35 to 60 Produce equine chorionic gonadotropin (eCG, PMSG) Sloughed off after day 60
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Zonary Placenta (bitch, queen)
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Discoid Placenta (human)
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Cell Layers Separating Maternal and Fetal Blood
Capillary Capillary Endothelium Endothelium Connective Tissue Connective Tissue Chorionic Epithelium Endometrial Epithelium
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Histological Classification
Tissues epithelial- syndesmo- endothelial- hemo- hemo- chorial chorial chorial chorial endothelial Maternal endothelium conn. tissue epithelium Fetal epithelium conn. tissue endothelium Species pig *ruminant dog human rat horse cat rabbit ruminant
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Important!!!! In all cases, fetal and maternal blood does not mix.
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