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Questions and Answers
Which structure forms when the somatopleure folds over the developing embryo?
Which structure forms when the somatopleure folds over the developing embryo?
What is the outer layer of the chorion called?
What is the outer layer of the chorion called?
What characterizes the choriovitelline placenta?
What characterizes the choriovitelline placenta?
Which component is primarily responsible for vascularization of the extra-embryonic membranes?
Which component is primarily responsible for vascularization of the extra-embryonic membranes?
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What happens to the yolk sac in most mammalian species?
What happens to the yolk sac in most mammalian species?
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How does the amnion behave in relation to the chorion in humans?
How does the amnion behave in relation to the chorion in humans?
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What is the primary role of the allantois in embryonic development?
What is the primary role of the allantois in embryonic development?
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What distinguishes the chorioallantoic placenta from the choriovitelline placenta?
What distinguishes the chorioallantoic placenta from the choriovitelline placenta?
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What is the primary function of the avascular amnion in embryo development?
What is the primary function of the avascular amnion in embryo development?
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Which extra-embryonic structure is primarily responsible for the exchange of gases and waste products?
Which extra-embryonic structure is primarily responsible for the exchange of gases and waste products?
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What is the role of the allantois during early embryonic development?
What is the role of the allantois during early embryonic development?
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The chorion is essential for what aspect of embryonic development?
The chorion is essential for what aspect of embryonic development?
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How does the process of implantation vary among species?
How does the process of implantation vary among species?
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What challenge is faced when assessing the timing of embryonic developmental events?
What challenge is faced when assessing the timing of embryonic developmental events?
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What is a common misconception about the function of extra-embryonic mesoderm layers?
What is a common misconception about the function of extra-embryonic mesoderm layers?
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What primary function does the highly vascular placenta serve in early pregnancy?
What primary function does the highly vascular placenta serve in early pregnancy?
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What primary role does the amnion serve during embryonic development?
What primary role does the amnion serve during embryonic development?
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Which extra-embryonic mesoderm layer is responsible for forming blood vessels and blood cells?
Which extra-embryonic mesoderm layer is responsible for forming blood vessels and blood cells?
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What structure develops as an outpouch of the hind-gut and stores urinary wastes?
What structure develops as an outpouch of the hind-gut and stores urinary wastes?
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What composition describes the yolk sac in mammals?
What composition describes the yolk sac in mammals?
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Which extra-embryonic membrane is crucial as the outermost layer and contributes to the development of the placenta?
Which extra-embryonic membrane is crucial as the outermost layer and contributes to the development of the placenta?
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The somatic mesoderm is associated with which of the following?
The somatic mesoderm is associated with which of the following?
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What is the primary characteristic of the chorion in terms of vascularity?
What is the primary characteristic of the chorion in terms of vascularity?
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How are the somatopleure and splanchnopleure primarily defined?
How are the somatopleure and splanchnopleure primarily defined?
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Study Notes
Extra-Embryonic Membranes and Placentation
- Vertebrate embryos require extra-embryonic membranes for development.
- Histotroph (uterine milk) nourishes the embryo before implantation.
- Somatopleure and splanchnopleure are mesoderm layers, with the somatopleure adjacent to the trophoblast.
- Extra-embryonic membranes develop from specific germ layers.
- Extra-embryonic tissues play a role before implantation.
- Vascularization of extra-embryonic membranes is crucial.
- Oxygenated and deoxygenated blood flow through different umbilical vessels.
- Placental types (epitheliochorial, endotheliochorial, hemochorial) exhibit differences in maternal-fetal circulation.
Introduction to Extra-Embryonic Membranes
- Extra-embryonic membranes form concurrently with embryonic development.
- Mesoderm migrates across the embryonic disc.
- Extra-embryonic regions develop.
- The embryo forms from three germ layers.
Extra-Embryonic Membranes Development
- Extra-embryonic mesoderm divides into two layers (somatic and splanchnic) forming somatopleure and splanchnopleure.
- Major derivatives of extra-embryonic membranes include the yolk sac, allantois, amnion, chorion.
- Yolk sac, allantois, are vascular.
- Amnion and chorion are avascular.
- Chorion is an outer layer playing a key placenta component.
Placentation Formation
- Development of the allantois. It forms from the hindgut, and expands until it surrounds the embryo.
- The amnion pinches off the embryo and forms a protective layer.
- Chorion forms from the remaining somatopleure after the formation of the amnion.
Vascularization of Extra-Embryonic Membranes
- Vascularization of extra-embryonic membranes is necessary for nutrient distribution.
- Splanchnopleure plays a role in forming vascular structures.
- Both chorion and amnion have mesoderm components but not fully vascularized.
Placental Types
- Choriovitelline and chorioallantoic placentas differ based on the source of the endoderm.
Species Differences in Placentation
- Time of implantation varies among species (e.g., 6 days in rodents vs. longer than a month).
- Different types of placentation: -Diffuse/microcotyledonary (pigs, horses) -Cotyledonary (ruminants) -Zonary (carnivores) -Discoid (rodents, humans)
- Number of layers separating maternal and fetal blood supplies varies.
Placental Barrier
- Six potential layers form the placental barrier (maternal endothelium, maternal connective tissue, maternal uterine epithelium, fetal chorionic epithelium, fetal connective tissue, and fetal capillary endothelium).
- Blood does not mix during pregnancy.
- Amount of tissue lost at parturition determines the necessary time for regeneration and fertility return.
Major Issues in Placentation
- Maintaining fetal nutrition and waste removal.
- Preventing immune rejection by the mother.
- Developing a complex structure for exchange.
- Embryonic tissue interaction with the maternal tissues.
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Description
Explore the fascinating roles of extra-embryonic membranes in vertebrate embryo development. This quiz covers their formation, the significance of histotroph, and the types of placentation. Delve into the complexities of maternal-fetal circulation and vascularization during early growth stages.
