Anatomy lecture 3
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Questions and Answers

Which germ layer is responsible for forming the central nervous system?

  • Endoderm
  • Mesoderm
  • Epiblast
  • Ectoderm (correct)
  • What is the correct order of germ layer formation during gastrulation?

  • Mesoderm, Ectoderm, Endoderm
  • Endoderm, Ectoderm, Mesoderm
  • Ectoderm, Endoderm, Mesoderm
  • Ectoderm, Mesoderm, Endoderm (correct)
  • Which structure does the mesoderm layer NOT contribute to?

  • Urinary system
  • Epidermis (correct)
  • Skeletal muscles
  • Cardiovascular system
  • What defines the body axes during the process of gastrulation?

    <p>Primitive Streak</p> Signup and view all the answers

    During gastrulation, where does the primitive streak form?

    <p>At the dorsal aspect of the bilaminar disc</p> Signup and view all the answers

    Which of the following structures is NOT formed by the endoderm?

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

    What type of cells migrate inwards during the process of gastrulation?

    <p>Epiblast cells</p> Signup and view all the answers

    Which germ layer is primarily responsible for forming the limbs?

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

    What is the primary outcome of teratogen exposure during the organogenic period?

    <p>Major birth defects</p> Signup and view all the answers

    Which of the following organs is derived from the endoderm?

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

    Which germ layer is responsible for forming the somite structures?

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

    Which of the following differentiates into the epidermis and related structures?

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

    During which embryological stage is cell differentiation and morphogenesis most critical?

    <p>Organogenic period</p> Signup and view all the answers

    What initiates the formation of the primary chorionic villi during the embryonic development process?

    <p>Cell division in cytotrophoblast</p> Signup and view all the answers

    Which structure facilitates gas and nutrient exchange between the embryo and maternal circulation?

    <p>Chorionic villi</p> Signup and view all the answers

    What is the primary driver of cranial and caudal folding during the 4th week of development?

    <p>Development of the neural tube</p> Signup and view all the answers

    During cephalocaudal folding, which structure is repositioned to the ventral surface of the embryo?

    <p>Primordial heart</p> Signup and view all the answers

    What anatomical feature does the endoderm contribute to during caudal folding?

    <p>Development of the hindgut</p> Signup and view all the answers

    What significant event occurs around day 21 or 22 of embryonic development?

    <p>First heartbeat of the embryo</p> Signup and view all the answers

    What is the primary structure formed from the fusion of the neural folds?

    <p>Neural tube</p> Signup and view all the answers

    Which of the following structures does the allantois contribute to during caudal development?

    <p>Urinary bladder</p> Signup and view all the answers

    Which layer of the embryo is primarily responsible for forming the cardiovascular system?

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

    What type of cells arise from the border of the neural fold during neural tube formation?

    <p>Neural crest cells</p> Signup and view all the answers

    Which process primarily describes the incorporation of embryonic tissues into the gut tube during development?

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

    Which type of somite is responsible for forming the dermis?

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

    The cephalocaudal folding results in the positioning of which two membranes in the embryo?

    <p>Oropharyngeal and cloacal membranes</p> Signup and view all the answers

    What is the correct order of steps involved in the formation of the neural tube?

    <p>Notochord induction, lateral edges rise, fusion of folds, neural crest cell migration</p> Signup and view all the answers

    What are the openings at the cranial and caudal ends of the neural tube called?

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

    From what mesodermal region do somites originate?

    <p>Paraxial mesoderm</p> Signup and view all the answers

    What is the function of the pericardial cavity within the intraembryonic coelom?

    <p>Surrounds the heart</p> Signup and view all the answers

    Which statement accurately describes the fate of neural crest cells after their detachment from the neural tube?

    <p>They form various structures including spinal ganglia.</p> Signup and view all the answers

    What is the role of the notochord in neural tube development?

    <p>It induces overlying ectoderm to thicken.</p> Signup and view all the answers

    What structure does the sclerotome ultimately differentiate into?

    <p>Bone and cartilage</p> Signup and view all the answers

    What primarily drives the lateral folding of the embryonic disc?

    <p>Differential growth of embryonic structures</p> Signup and view all the answers

    What layers of mesoderm are involved in the formation of body cavities during lateral folding?

    <p>Somatic and splanchnic mesoderm</p> Signup and view all the answers

    Which part of the future digestive system is mostly formed by the endoderm during lateral folding?

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

    What key role does the splanchnic mesoderm play during the folding process?

    <p>It envelopes the gut tube</p> Signup and view all the answers

    What is the primary difference in the roles of endoderm and ectoderm during lateral folding?

    <p>Endoderm interacts with mesoderm, while ectoderm does not</p> Signup and view all the answers

    During lateral folding, what structure is formed as a result of the intraembryonic coelom?

    <p>Thoracic and abdominal cavities</p> Signup and view all the answers

    Which embryonic structure is heavily influenced by the interaction of the endoderm and splanchnic mesoderm?

    <p>Gut tube</p> Signup and view all the answers

    What initiates the inward and downward movement of the lateral edges of the embryo?

    <p>Mechanical forces from somite growth</p> Signup and view all the answers

    Which embryonic layer remains on the exterior and forms structures related to the nervous system?

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

    Study Notes

    Overview of Gastrulation

    • Gastrulation forms the trilaminar structure of the embryo, establishing primary germ layers: ectoderm, mesoderm, and endoderm.
    • Marks the onset of the embryonic period and establishes body orientation independent of the mother's position.

    Germ Layers and Their Locations

    • Ectoderm (Outer Layer):
      • Forms the external epithelial lining including the CNS (brain, spinal cord) and epidermis (skin, hair, nails), as well as sensory organs.
    • Mesoderm (Middle Layer):
      • Located in muscle and connective tissue, developing into skeletal muscle, bones, cardiovascular system, urinary and reproductive systems.
    • Endoderm (Inner Layer):
      • Forms internal epithelial linings, including respiratory and digestive tract tissues, and accessory digestive organs.

    Process of Gastrulation

    • Formation of the Primitive Streak:
      • Appears in the epiblast, establishing the body axes; cells begin to migrate inward.
    • Cell Migration:
      • Ectoderm thickens to form the neural tube with neural crest cells contributing to the peripheral nervous system structures.

    Somite Development

    • Somites are cuboidal clumps of mesoderm derived from paraxial mesoderm.
    • Forms structured derivatives:
      • Sclerotome: bone and cartilage
      • Myotome: skeletal muscle
      • Dermatome: dermis

    Intraembryonic Coelomic Spaces

    • Coelomic spaces form small cavities within the lateral plate mesoderm leading to the development of paracardial, peritoneal, and pleural cavities.
    • The lead to the creation of body cavities that house essential organs.

    Cephalocaudal Folding

    • Occurs in early week 4, characterized by cranial and caudal regions folding inward.
    • Driven by differential growth rates of the neural folds, facilitating the formation of the head (cephalic) and tail (caudal) regions.
    • Integrates endoderm into the coelomic space, forming the hindgut and the urinary bladder.

    Lateral Folding

    • Lateral (transverse) folding transforms the flat embryo into a cylindrical structure by fusing the left and right lateral edges.
    • Driven by the growth of the somites and the convergence of lateral plate mesoderm.
    • Contributes to the formation of the foregut, midgut, and the body cavities.

    Comparative Roles of Endoderm and Ectoderm During Folding

    • Endoderm:
      • Forms the gastrointestinal tract and associated organs, plays a critical role during folding.
    • Ectoderm:
      • Remains external, forming skin and nervous system components; key in neural tube formation.

    Teratology

    • Study of abnormal development causes, mechanisms, and patterns.
    • Developmental stages, especially organogenesis (weeks 4-8), are highly susceptible to teratogen exposure leading to defects.

    Major Germ Cell Derivatives

    • Endoderm: Forms internal linings of the gastrointestinal and respiratory tracts, liver, pancreas, and urinary system.
    • Mesoderm: Develops into the musculoskeletal system, cardiovascular system, kidneys, and gonads.
    • Ectoderm: Generates CNS, PNS, skin, sensory organs, and associated tissues.

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    Description

    This quiz covers the essential aspects of gastrulation, including the formation of the trilaminar structure of the embryo and the establishment of the primary germ layers: ectoderm, mesoderm, and endoderm. It also highlights the significance of these layers in developing various organ systems during the embryonic period.

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