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Published byCaren Camilla Oliver Modified over 9 years ago
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Early Vertebrate Development Early Development of Mammals Early Development of Birds…if we have time.
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Long and Winding Road… Both Egg and Sperm have to overcome physical barriers. Ampulla- site of fertilization.
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Cleavage in Mammals Rotational cleavage – 1 st Meriodionally – 2 nd one divides meriodionally, one divides equatorially Asynchrony No real Mid-Blastula Transition.
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Compaction Division of early embryo up to 8 cell stage is loosely arranged. At 8 cell stage, cells form tight interactions and divide into 16 cell morula. Internal Cells= Internal Cell mass (ICM) Most external cells become trophoblast.
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Early Cells in Mammalian Embryo Totipotent Pluripotent
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Cavitation. Trophoblast cells secrete fluid into Morula: blastocoel Trophoblast Na + pumps are activated by oviduct cells.
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Hatching of Mammalian Blastula Zona pellucida prevents embryo from attaching to oviduct wall. Trypsin like protease: releases embryo from ZP.
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Mammalian Gastrulation Mother provides nutrients The reliance of embryo on Mother has resulted in fetal organs – Chorion – Hypoblast/epiblast – Germ disc – Amniotic cavity
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Mammalian Gastrulation: Primative Groove
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Extraembryonic Membranes Trophoblast cells make up cytotrophoblast and syncytiotrophoblast. Trophoblasts and Uterine tissue: Placenta
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Axis specification in Mammals Two signaling centers – Node – Anterior Visceral Endoderm(AVE) Work together to form anterior region. Notochord: dorsal infolding of small ciliated cells AVE: visceral endoderm migrates forward. Antagonists of Nodal – Lefty-1; Cerberus – Nodal activates expression of posterior genes; Lefty-1 and Cerberus blocks this activity
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Axis Specification: Anterior-Posterior positioning FGF and Retinoic acid gradients. Ultimately leads to differential expression of Hox genes
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Anterior-Posterior Axis: Hox Code
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Retinoic Acid and Hox Gene Expression
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Dorsal-Ventral and Left-Right Axes DV axis formation: Poorly characterized. Left-right axis formation: Nodal and Pitx2
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Early Development of Birds: Cleavage
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Gastrulation: Birds The Hypoblast The primative streak
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The Primitive Streak
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Primitive Streak: Molecular mechanisms of migration
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Regression of Primitive streak
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Axis specification in Birds Gravity and PMZ
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Left Right Axis
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