Gastrulation in Embryonic Development
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Gastrulation in Embryonic Development

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Questions and Answers

What is formed during the first week of implantation?

  • Embryoblast differentiation into epiblast and hypoblast
  • Formation of blastocyst when fluid secreted within morula forms a cavity (correct)
  • Development of cytotrophoblast and syncytiotrophoblast
  • Degeneration of the zona pellucida (ZP)
  • Which structures differentiate from the trophoblast during the implantation process?

  • Ectoderm and mesoderm
  • Embryoblast and extraembryonic mesoderm
  • Cytotrophoblast and syncytiotrophoblast (correct)
  • Amnion and allantois
  • What condition is associated with the loss of mesoderm during gastrulation?

  • Ectopia cordis
  • Spina bifida
  • Sacrococcygeal teratoma
  • Sirenomelia (correct)
  • During which week of implantation does the bilaminar embryo form?

    <p>Second week</p> Signup and view all the answers

    What component links the embryo to the trophoblast in mammals?

    <p>Umbilical cord</p> Signup and view all the answers

    What is the primary characteristic of gastrulation during embryonic development?

    <p>Movement of cells to form three germ layers</p> Signup and view all the answers

    What changes occur during the cellular differentiation stage of gastrulation?

    <p>Cells begin to follow specific morphogenetic movements</p> Signup and view all the answers

    Which of the following processes is NOT considered a morphogenetic movement during gastrulation?

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

    In protostomes, what does the first opening in the embryo develop into?

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

    What is the significance of Hensen's node during avian gastrulation?

    <p>It serves as the primary site for cell migration</p> Signup and view all the answers

    How does the role of the nucleus change during the gastrulation stage?

    <p>It gains more impact in controlling development</p> Signup and view all the answers

    Which layer forms the epiblast and primary hypoblast during avian gastrulation?

    <p>Area pellucida</p> Signup and view all the answers

    What defining event marks the onset of gastrulation in vertebrates?

    <p>Initiation of morphogenetic movements</p> Signup and view all the answers

    Study Notes

    Gastrulation

    • First described by Ernst Hackel in 1872
    • The most defining event in the third week of gestation
    • A process where cells undergo morphogenetic movements
    • Formation of three germ layers: ectoderm, mesoderm, and endoderm

    Character of Gastrulation Stage

    • The first stage of cellular differentiation
    • Embryonic cells begin to follow specific layers through morphogenetic movements
    • Cellular division loses synchronization and coordination becomes dominant over metabolic changes
    • Nucleus plays a more significant role in the process of development control compared to the previous stages
    • Chromosomes are more actively involved than before in controlling development

    Morphogenetic Processes

    • Invagination: Infolding of a sheet of cells
    • Involution: Inward movement of a cell sheet over the surface of another cell sheet
    • Ingression: Migration of individual cells into the interior of the embryo
    • Delamination: Splitting of one cell sheet into two
    • Epiboly: The spreading or expansion of a cell sheet over other cells

    Protostomes and Deuterostomes

    • Protostomes: The first opening in the embryo becomes the mouth
    • Deuterostomes: The first opening in the embryo becomes the anus

    Axis Formation

    • Defines the anterior-posterior and dorsal-ventral axes of the embryo
    • Occurs through a series of cell movements and signaling events

    Fish Gastrulation

    • Epiboly of blastoderm cells over the yolk
    • Deep cells move outwardly to intercalate with superficial cells
    • YSL: Yolk Syncytial Layer
    • EVL: Enveloping Layer
    • Germ Ring: The ring of cells that forms at the margin of the blastoderm

    Amphibian Gastrulation

    • The blastopore forms at the vegetal pole of the blastula
    • Cells move through the blastopore to form the mesoderm and endoderm
    • Dorsal Lip: The dorsal-most region of the blastopore

    Avian Gastrulation

    • Area Pellucida: The region of the blastoderm that will form the embryo
    • Forms the epiblast and primary hypoblast through delamination
    • Posterior cell sheets migrate anteriorly to form the secondary hypoblast
    • Primitive Streak: A thickening of the epiblast that forms in the posterior region of the embryo
    • Primitive Groove: A depression within the primitive streak
    • Hensen’s Node: The anterior end of the primitive streak
    • Primitive Pit: A funnel-shaped depression where cells can pass through

    Mammalian Gastrulation

    • Similar to avian gastrulation but with a more complex process
    • Involves formation of extraembryonic membranes and the embryo
    • Trophoblast: The outer layer of the blastocyst
    • ICM: Inner Cell Mass
    • Embryoblast: The part of the ICM that will form the embryo

    Clinical Correlation

    • Sirenomelia: Loss of mesoderm (caudal dysgenesis)
    • Sacrococcygeal Teratoma: Remnant of the primitive streak

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    Description

    This quiz explores the critical stage of gastrulation in embryonic development, detailing its processes and significance. Key topics include the formation of the three germ layers and the morphogenetic processes involved. Test your knowledge on cellular differentiation and the role of the nucleus during this vital phase.

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