Lecture 19 Placentation and Maternal Recognition of Pregnancy

Lecture 19 Placentation and Maternal Recognition of Pregnancy Animal Science 434 John J. Parrish

Blastulation Gap Junctions Inner Cell Mass Na+ Zona Pellucida [Na+] Trophectoderm H 2 O Tight Junctions

Hatching l Bovine » 9 - 11 days l Equine, Ovine » 7 - 8 days l Porcine » 6 days

Conceptus Growth Occurs in cow, pig and sheep Spherical Tubular Filamentous Cow • Day 15, 1 -2 mm • Day 18 -19, 10 -20 cm Embryonic Area Elongating Trophoblast Mare remains spherical!

Development of Porcine Conceptuses from Day 10 to 12 5 mm Spherical 10 mm Spherical Inner Cell Mass 15 mm Tubular 150 mm Filamentous

Elongated Day 15 Porcine Conceptus Embryo

Uterine Location of Elongating Ruminant Blastocyst Bovine and Ovine Corpus Luteum

Pig Intrauterine Migration Day 5

Pig Intrauterine Migration Day 7

Pig Intrauterine Migration Day 12 Embryos become fixed Transuterine migration is rare in cow and ewe!

Trans-uterine Migration in the Mare Begins Day 10 Fixation can occur in either horn! Fixation on day 15 - 16 Corpus Luteum

Gastrulation Trophectoderm Inner Cell Mass Formation of Germ Layers Endoderm Blastocoele Cavity

Gastrulation Endoderm Yolk Sack

Gastrulation Endoderm Yolk Sack

Gastrula Ectoderm Trophectoderm Endoderm

Gastrula Ectoderm Extraembryonic Coelom Mesoderm Yolk Sack Endoderm Trophectoderm (Chorion)

Germ Layers l Ectoderm l Mesoderm l Endoderm » CNS » Circulatory » Digestive » Sense organs » Skeletal » Liver » Mammary » Muscle » Lungs glands » Reproductive » Pancreas » Sweat glands tracts » Thyroid gland » Skin » Kidneys » Other glands » Hair » Urinary ducts » hooves

Embryonic Ectoderm Placenta Formation Amniotic Folds Extraembryonic Ceolom Yolk Sack Trophectoderm Mesoderm Chorion Endoderm

Amniotic Fold Amniotic Cavity Allantois Yolk Sack Extraembryonic Ceolom Chorion

Amnionic Cavity Yolk Sack Amnion Uterine Lumen Allantois Chorion Extraembryonic Ceolom Carnuncle

Chorion Amniotic Cavity Amnion Allantois Cavity Yolk Sack Allantochorion (Chorioallantois) Cotyledon

Placental Membranes l Yolk Sack » In birds to nourish embryo » In mammal atrophies but source of blood cells and primordial germ cells l Amnion » Non-vascular, fluid filled » Fluid produced by fetus » Protective cushion » Ruptures at birth (not breaking of water)

Placental Membranes (cont. ) l Allantois » Blood vessels » Fuses with chorion • Allantochorion or chorioallantois • Brings blood vessels to chorion l Chorion » Outermost membrane » Attachment to mother

Maternal Recognition of Pregnancy

Luteal Regression PGF 2 a (Bovine, Ovine, Porcine) PGF 2 a (Equine) No Uterine Factor (human)

CL Status CA CL (+) Uterine PGF 2 a Filamentous Embryo (+) Maintained Mechanisms CL Regression • Luteolytic • No CL support CL Maintenance • Antiluteolytic » Block PGF 2 a effects • Luteotrophic » Stimulate progesterone production by CL

Recognition of Pregnancy Conceptus Secretions • Proteins • Steroids

Recognition of Pregnancy in Bovine and Ovine Mechanism • Antiluteolytic • Inhibit oxytocin receptor synthesis • Inhibit PGF 2 a synthesis Conceptus Secretions • Interferons • o. IFN-t • b. IFN-t Critical Days • Bovine - 16 to 17 • Ovine - 12 to 13

Recognition of Pregnancy in the Porcine PGF 2 a

Recognition of Pregnancy in the Porcine E 2 E 2 E 2 PGF 2 a

Recognition of Pregnancy in the Porcine Conceptus Secretions • Estradiol E 2 Critical Days PGF 2 a E 2 PGF 2 a 11 to 12 E 2 PGF 2 a Mechanism • Antiluteolytic » Redirect PGF 2 a » Requires 2 embryos per horn

Recognition of Pregnancy in the Mare PGF 2 a Conceptus Secretion • ? Critical Days 10 to 14 PGF 2 a Mechanism • antiluteolytic

Recognition of Pregnancy in the Human Conceptus Secretes • HCG Mechanism • luteotrophic HCG Critical Days • 8 to 12

Recognition of Pregnancy INF-t Conceptus Secretions • Proteins • Steroids HCG Estradiol

Dog and Cat l CL does not regress if not pregnant » no uterine effect l Psuedopregnancy » CL last similar length as in pregnancy

Implantation

Time of Implantation Attachment to Uterus Species Beginning Completion pig 13 24 cow 22 40 sheep 15 28 mare 24 - 40 95 - 100 human 7 -8 30

Type of Implantation l Superficial » Chorion lies opposed to uterine wall » Farm animals l Eccentric » Chorionic sack in a uterine fold » Rodent l Interstitial » Embryo digests part of uterine wall » human

Degree of Tissue Loss at Parturition l Deciduate » Eccentric, interstitial » Rodent, human l Indeciduate or Nondeciduate » Superficial » Farm animals

Shape or Distribution of Chorionic Villi l Cotelydonary - cow, sheep l Diffuse - pig, horse l Zonary - dog, cat l Discoid - human

Cotelydonary Placenta Cow Convex Cotelydon (Chorion) Ewe Concave Caruncle 70 - 120 Endometrium 90 - 100

Cotelydonary Placenta Cow Placentome Ewe

Placental Attachment in Ruminant Binucleate Cell Chorion Migrate and fuse with uterine epithelium Uterine Epithelium Syncytium Capillary Stroma Fusion of Binucleate cells and uterine epithelium (multinucleate)

Day 23 Migration of Bicnucleate Cells and Formation of Syncytium Binucleate Cell Endometrial Stroma Multinucleated Cells in Uterine Epithelium

Binuclear Giant Cells l 20% of fetal placenta l Invade endometrium l Source » Placental lactogen » Pregnancy specific protein B

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

Pregnancy Specific Protein B l Unique to ruminants l Function uncertain l Has been used to detect pregnancy » Cattle, sheep, deer • Can be used to detect pregnancy in cows after day 25 » Not early pregnancy factor!!!

Diffuse Placenta Horse Pig Microcotyledons

Microcotelydons Microcotelydon (Fetal) Increase placental surface area Microcotelydon Epithelium Endometrial Glands Uterine Arteries Endometrium Microcotelydon (Maternal) Uterine Veins

Endometrial Cups in Mare l From both trophoblast and endometrium l 5 to 10 l Form between days 35 to 60 l Produce equine chorionic gonadotropin (e. CG, PMSG) l Sloughed off after day 60

Zonary Placenta (bitch, queen)

Discoid Placenta (human)

Cell Layers Separating Maternal and Fetal Blood Fetal Maternal Capillary Endothelium Connective Tissue Chorionic Epithelium Connective Tissue Endometrial Epithelium

Histological Classification Tissues syndesmochorial endothelialchorial hemoendothelial Maternal endothelium + conn. tissue + epithelium + + + - - - Fetal epithelium + conn. tissue + endothelium + + + *ruminant dog cat human rat rabbit Species epithelialchorial pig horse ruminant

Important!!!! l In all cases, fetal and maternal blood does not mix.