Basic Medical Science II: Embryology Week 2
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Questions and Answers

Which layer of the trophoblast differentiates into two layers during day 8 of development?

  • Trophoblast (correct)
  • Blastocyst
  • Syncytiotrophoblast
  • Embryoblast
  • The cytotrophoblast is a multinucleated zone without clear cell boundaries.

    False (B)

    What are the two layers that the embryoblast differentiates into during day 8?

    Hypoblast and epiblast

    The ______ is partially embedded in the endometrial stroma on day 8 of development.

    <p>blastocyst</p> Signup and view all the answers

    Match the following structures with their correct description on day 8 of development:

    <p>Syncytiotrophoblast = Multinucleated zone without clear cell boundaries Cytotrophoblast = Mononucleated cells within the trophoblast Epiblast = Layer of high columnar cells near the amniotic cavity Hypoblast = Layer of small cuboidal cells near the blastocyst cavity</p> Signup and view all the answers

    What is the flat disc formed by the two layers of the embryoblast during day 8 called?

    <p>Bilaminar embryonic disc (D)</p> Signup and view all the answers

    The cells in the cytotrophoblast divide and migrate into the syncytiotrophoblast on day 8.

    <p>True (A)</p> Signup and view all the answers

    What is the small cavity that appears within the epiblast during day 8?

    <p>Amniotic cavity</p> Signup and view all the answers

    On day 8, the blastocyst is _____.

    <p>deeply embedded in the endometrium (B)</p> Signup and view all the answers

    The exocoelomic membrane is formed by the cytotrophoblast.

    <p>False (B)</p> Signup and view all the answers

    What is the name of the cavity that forms within the blastocyst on day 8?

    <p>Exocoelomic cavity (primitive yolk sac)</p> Signup and view all the answers

    The vacuoles that appear in the syncytiotrophoblast on day 8 eventually merge to form large ______.

    <p>lacunae</p> Signup and view all the answers

    Match the germinal layer with its derived structure:

    <p>Hypoblast = Exocoelomic membrane Epiblast = Amniotic cavity Syncytiotrophoblast = Lacunae</p> Signup and view all the answers

    What are the two layers that the trophoblast differentiates into?

    <p>Cytotrophoblast and Syncytiotrophoblast (B)</p> Signup and view all the answers

    The amniotic cavity is formed within the epiblast.

    <p>True (A)</p> Signup and view all the answers

    What is the name of the thin membrane formed by the hypoblast?

    <p>Exocoelomic membrane or Heuser's membrane</p> Signup and view all the answers

    The _____ cells near the cytotrophoblast are called amnioblasts.

    <p>epiblast</p> Signup and view all the answers

    Match the following terms with their descriptions:

    <p>Syncytiotrophoblast = Multinucleated zone formed by the trophoblast Cytotrophoblast = Mononucleated zone of the trophoblast Hypoblast = Layer of small cuboidal cells within the embryoblast Epiblast = Layer of high columnar cells within the embryoblast Amniotic Cavity = Cavity that forms within the epiblast</p> Signup and view all the answers

    What happens to the vacuoles within the syncytiotrophoblast?

    <p>They fuse to form large lacunae (A)</p> Signup and view all the answers

    The blastocyst becomes deeply embedded in the endometrium by day 9.

    <p>True (A)</p> Signup and view all the answers

    What is the name of the defect in the surface epithelium that is closed by a fibrin coagulum during implantation?

    <p>Penetration defect</p> Signup and view all the answers

    Flashcards

    Exocoelomic Membrane

    A membrane formed by the fusion of vacuoles in the syncytiotrophoblast, contributing to the formation of the primitive yolk sac.

    Exocoelomic Cavity

    The space within the exocoelomic membrane, also known as the primitive yolk sac, important for early embryonic development.

    Hypoblast

    A layer of flattened cells that forms the inner lining of the exocoelomic cavity and contributes to the formation of the yolk sac.

    Syncytiotrophoblast

    A multi-nucleated tissue formed by the fusion of trophoblast cells, involved in the implantation and nutrient exchange with the mother.

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    Heuser's Membrane

    A membrane that forms from the hypoblast layer and lines the exocoelomic cavity, crucial for early embryonic structure.

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    Blastocyst

    A structure formed in the early development of mammals that implants into the endometrium.

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    Day 8 development

    On Day 8, the blastocyst is partially embedded in the endometrial stroma.

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    Trophoblast layers

    The trophoblast differentiates into two layers: cytotrophoblast and syncytiotrophoblast.

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    Cytotrophoblast

    The inner layer of the trophoblast that is mononucleated and can divide.

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    Embryoblast

    The inner cell mass that differentiates into two layers: hypoblast and epiblast.

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    Epiblast

    The upper layer of the embryoblast; consists of high columnar cells.

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    Amniotic cavity

    The space that enlarges to contain amniotic fluid.

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    Amnioblasts

    Cells derived from the epiblast that contribute to the amniotic cavity.

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    Lacunar stage

    A stage in development when vacuoles in the syncytiotrophoblast fuse to form large lacunae.

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    Study Notes

    Presenter Information

    • Presenter: Dr. Eman El Sawaf
    • Affiliation: Anatomy & Embryology Department, Faculty of Medicine, Helwan University

    Topic Overview

    • Module: Basic Medical Science II
    • Subtopic: Anatomy and General Embryology

    Embryological Development

    • The presentation focuses on development events during the second week (days 8 and 9) of gestation
    • Specifically, the topic covers the bilaminar germ disc stage of embryonic development

    Day 8 Blastocyst

    • Implantation: The blastocyst is partially embedded into the endometrial stroma.
    • Trophoblast differentiation: The trophoblast differentiates into two layers:
      • Cytotrophoblast (mononucleated cells)
      • Syncytiotrophoblast (multinucleated zone without clear cell boundaries)
    • Embryoblast differentiation: The inner cell mass (embryoblast) differentiates into two layers:
      • Hypoblast (small cuboidal cells near the blastocyst cavity)
      • Epiblast (high columnar cells near the amniotic cavity)
    • Formation of the Bilaminar embryonic disc: The two layers (hypoblast and epiblast) form a flat disc
    • Amniotic Cavity Formation: A small cavity appears within the epiblast, growing to become the amniotic cavity. Cells near the cytotrophoblast are called amnioblasts

    Day 9 Blastocyst

    • Implantation: The blastocyst is deeply embedded within the endometrium.
    • Defect closure: The penetration defect in the surface epithelium is closed by a fibrin coagulum.
    • Syncytiotrophoblast vacuoles: Vacuoles appear in the syncytiotrophoblast.
    • Formation of large lacunae: When the vacuoles fuse, they form large lacunae.
    • Lacunar stage: This marks a stage in the formation of the embryonic circulation.
    • Exocoelomic membrane: The hypoblast forms a thin membrane called the exocoelomic (Heuser) membrane, (flattened cells).
    • Exocoelomic cavity (primitive yolk sac): The exocoelomic membrane delineates the exocoelomic cavity, which is the primitive yolk sac.

    Other Important Points

    • Objectives: Students should be able to describe the events in the second week of development.
    • Reference: Langman's Medical Embryology 13th Edition by T.W. Sadler is cited as a reference source.

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    Description

    This quiz covers the key concepts of embryological development during the second week of gestation, focusing on the bilaminar germ disc stage. It delves into the specifics of implantation, trophoblast differentiation, and the development of embryoblast layers. Test your understanding of these foundational processes in anatomy and embryology.

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