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21 Cards in this Set
- Front
- Back
What process occurs in the first two weeks of pregnancy?
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Embryogenesis
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What are the basic goals of embryogenesis?
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• From fertilization to a successful uterine implantation: the development of placental precursors and the embryonic bi-laminar disk
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What are the first few steps of embryogenesis?
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1. 8th day - blastocyst partially embedded in the uterine wall
2. Syntrophoblasts continue to invade the uterine wall 3. Form a Fibrin Plug (a woman can spot at her normal cycle time, but its not a real period 4. Differentiation of (embryoblast) embryonic disc into 2 layers: • Epiblast • Hypoblast |
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1. Epiblast?
2. Hypoblast |
1. A COLUMNAR cell layer facing the cytotrophoblast (closest to the cavity)
2. A CUBOIDAL cell layer facing the blastocyst cavity (outside the epiblast) |
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Amniotic Cavity
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Space between the epiblast and the cytotrophoblast
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Amnioblasts
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• Formed from the cytotrophoblasts
• Line the upper region of the amniotic cavity |
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What do cytotrophoblasts form?
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• amnioblasts and Heuser's membrane
• extraembryonic mesoderm |
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What is Heuser's Membrane?
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Membrane that surrounds the original blastocyst cavity. Now the cavity is called the Primary Yolk Sac
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What does the Blastocyst Cavity become?
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The Primary Yolk Sac
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The extraembryonic mesoderm is made up of two parts:
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• Extraembryonic Somatic Mesoderm
• Extraembryonic Splanchnic Mesoderm |
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What does the Extraembryonic Somatic Mesoderm line?
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Inner surface of the cytrotrophoblast
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What is the Chorion?
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Formed by the Extraembryonic Somatic Mesoderm and the two layers of trophoblasts
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What does the Extraembryonic Splanchnic Mesoderm line?
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Lines the trophoblasts (outer surface of the yolk) and covers the amnion
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What do Syntrophoblasts do?
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• Grow all over and develop spaces called Lacunae
• They eventually establish Uteroplacental Circulation |
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When does the Extraembryonic Mesoderm form?
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Middle of the second week
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What are the Maternal Blood Sinusis?
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They are filled with the mother's blood and flow into the sytrophoblastic lacunae on the 12th day allowing primitive uteroplacental circulation
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What does the primary yolk sac become?
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The secondary yolk sac
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1) What is the secondary yolk sac lined by?
2) When does the secondary yolk sac form? |
1) Heuser's membrane
2) After the extraembryonic membrane and extraembryonic coelom form a cavity |
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Primary Stem Villi
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Extensions of cytotrophoblast that grow out into the blood-filled lacunae (covered by syntrophoblasts)
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Cytotrophoblasts give rise to:
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1. Amnioblast
2. Heuser's Membrane 3. Extraembryonic Membrane (2 layers, 1 space [extraembryonic coelom]) 4. Forms column of cells (primary stem villi) |
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What are the 3 spaces formed during the second week of development?
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1. Amniotic Cavity - spaces between amnioblast and embryoblast
2. Primary Yolk Sac - Blastocyst lined by Heuser's membrane 3. Secondary Yolk Sac - primary yolk sac lined by Heuser's membrane |