Anatomy_Thorax_Review - 1 THE THORAX AND...

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Unformatted text preview: 1 THE THORAX AND EARLY EMBRYOLOGY • Early Embryologic Development • Bones / General Regions of the Thorax • The Breast • Musculature of the Thorax • Nerve and Blood Supply to the Intercostals • Embryological Partitioning of Body Cavities • The Lungs • Fundamentals of Radiology • Embryology of the Heart • Pericardium and Positioning of the Heart • The Heart • The Superior Mediastinum • Tetralogy of Fallot EARLY EMBRYONIC DEVELOPMENT Morula: The name of the embryo at the 16 to 32 cell stage. Blastocyst : At about day 5 after implantation. • Cells are divided into the inner cell mass and trophoblast. • Inner Cell Mass: The cells on the inside. • Trophoblast: The cells surrounding the outside. Implantation: Blastocyst travels from ampulla ------> oviduct ------> uterus to implant in the uterus. Implantation occurs around day 5. Trophoblast forms two cell-layers. • Syncytiotrophoblast: The cell mass at the embryonic pole (nearest the uterine wall). • Cytotrophoblast: The cell mass jutting out from the pole. Will form the extraembryonic membranes. Inner Cell Mass: Form two layers of cells, epiblast and hypoblast. A Bilaminar Embryonic Disc is formed. • Epiblast Cells: From inner cell mass, will ultimately give rise to the three germ layers and the entire embryo. • Amniotic Cavity : Forms as the space between the Epiblast and cytotrophoblast.. • Hypoblast Cells: These cells are the first to migrate and eventually disintegrate. Progression of events after implantation: Each item represents simultaneous events. • The epiblast cells grow deeper into the wall of the uterus. o The amniotic cavity begins to form in the epiblast layer . • Amnioblasts differentiate from the epiblasts and migrate to the inner amniotic layer. o Heuser's Membrane is formed from hypoblasts (interior of cytotrophoblast layer). It will differentiate into the yolk sac. o Trophoblastic Lacunae are openings that form in the syncytiotrophoblast. • Maternal blood enters the lacunae. o Extraembryonic Reticulum forms. • Primary Yolk Sac: Epiblasts form mesoderm on the exterior of Heuser's Membrane. • Definitive Yolk Sac: New Hypoblast cells migrate to displace Heuser's membrane, pushing back the primary yolks sac to form the new definitive yolk sac. o Chorionic Cavity forms in the ECM. 2 • The Placenta is formed from a network of villi (trophoblast cells). Villi form from trophoblast in the following order of maturation: o Primary Villus : Cytotrophoblast + a layer of syncytiotrophoblast grow into the lacunae. o Secondary Villus : Extraembryonic mesoderm grows into the primary villus. o Tertiary Villus : Extraembryonic mesoderm gives rise to blood vessels. Exchange of nutrients is now possible with mother ....
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This note was uploaded on 01/30/2011 for the course BIO 210 taught by Professor S during the Spring '10 term at University of Toronto.

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Anatomy_Thorax_Review - 1 THE THORAX AND...

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