Placentation- Lecture 11 Flashcards
Fetal membranes definition
Membranes that function for the protection or nourishment or respiration or excretion of a developing fetus. Yolk sac, amnion, allantois and chorion (chorioallantois).
Cotyledonary placenta
Seen in ruminants (ewe and cow). Meternal caruncle+ fetal cotyledon= placentome.
Roles of the placenta
Nutrient exchange. Gas exchange. Stores waste. Protective. Endocrine organ.
Zonary (Single vs. Double)
Single: Attachment in a ring, dog and cat. Double: Attachment in two bands, ferret and raccoon.
Epitheliochorial
5-6 layers. Seen in mare, sow, cow, sheep, goat (ruminant species). Partial and transient erosions of the endometrium. Binucleate cells.
Deciduate
Loss of maternal tissue at parturition. Seen in carnivores, humans and rodents.
Chorion
Attaches to uterus and absorbs nutrients. Maternal interface. Allows maternal/fetal gas exchange. Produces hormones.
Primate placenta
Discoid. Hemochorial. Trabecular. Deciduate.
Synepitheliochorial
Transiently 5 layers
Amnion
Protects fetus from injury. Provides lubrication for parturition. Reservoir for urine and wastes. Nutrient exchange.
Mare placenta
Diffuse placenta. Microcotyledons. Adeciduate.
Metatherian
Choriovitelline placenta (yolk sac placenta). Marsupials.
3 layers
Fetal: Endothelium, CT, epithelium. Maternal: 0
Placenta definition
The vascular organ formed in the uterus during pregnancy, consisting of both maternal and embryonic/fetal tissues and providing oxygen and nutrients for the fetus and transfer of waste products from the fetal to the maternal blood circulation.
Binucleate cells
Found in epitheliochorial placentas. Giant cells. Chorionic origin. Fuse with maternal epithelium. Placental lactogen. Specific proteins.
Sow placenta
Diffuse placenta. Necrotic tips. Folded with areolae.
Non-deciduate/Adeciduate
Non-invasive. Complete separation of maternal and fetal tissues. Seen in sow, mare (ruminants). Seen in diffuse and epitheliochorial placenta.
4 layers
Fetal: Endothelium, CT, Epithelium. Maternal: Endothelium.
Implantation
Attachment of the placenta to the uterus. Sow- least number of days to implant. Mare- highest number of days to implant.
Allantois
Fuses with chorion. Carries blood vessels of placenta. Blood supply for chorion. Reservoir for nutrients and wastes. Umbilical cord attaches fetus to allantois.
Hemochorial
3 layers. Seen in primates and rodents.
Carnivore species placenta
Zonary. Endotheliochorial. Labyrinthine. Deciduate. Canine- marginal hematomas, stagnant maternal blood, hemoglobin is converted to green uteroverdin at parturition.
Ruminant species placenta
Cotyledonary. Epitheliochorial. Villous. Adeciduate.
Diffuse placenta
Villi diffusely covering the whole surface of the chorion. Seen in swine and horses.
Placental classification
Distribution of contact areas- shape. Tissue layers separating maternal and fetal blood-invasion. Degree of interdigitation of the vasculature. Maternal tissue loss at birth.
Interdigitation
Folded type- pig. Lamellar type- horse (microcotyledons). Trabecular type- human. Villous type- cow. Labyrinthine type- dog.
Endotheliochorial
4-5 layers. Seen in carnivores.
Eutherian
Chorioallantoic placenta. The rest of us.
6 layers
Fetal: Endothelium, CT, Epithelium. Maternal: Epithelium, CT, Endothelium.
Yolk sac
Early nutrition supply for early embryo.
5 layers
Fetal: Endothelium, CT, Epithelium. Maternal: CT, Endothelium.
Prototherian
Egg-laying. Platypus, echidnas.
Discoid
One or two attachment spots. Seen in monkey, man and rodents.
