Human Embryology Week 4 Overview
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Questions and Answers

What is formed as a result of the folding of the neural plate?

  • Limb Buds
  • Neural Tube (correct)
  • Somites
  • Pharyngeal Arches

    • What key structures develop from somites?

  • Vertebrae and Ribs (correct)
  • Limb Muscles Only
  • Digestive Organs
  • Eyes and Ears

    • Which of the following conditions is associated with problems in neural tube formation?

  • Holoprosencephaly
  • Cleft Palate
  • Anencephaly (correct)
  • Hirschsprung Disease

    • What developmental potential do limb buds have?

    <p>To develop into arms and legs (D)</p> Signup and view all the answers

    Which part of the neural tube undergoes cranial closure first?

    <p>Cranial End (C)</p> Signup and view all the answers

    What type of cells are formed from the folds of the neural tube?

    <p>Neural Crest Cells (C)</p> Signup and view all the answers

    How many somites typically form during Week 4 of development?

    <p>20-25 (A)</p> Signup and view all the answers

    Which embryonic structure primarily determines the segmented body plan of the embryo?

    <p>Somites (D)</p> Signup and view all the answers

    What structures are primarily formed from the sclerotome component of the somite?

    <p>Vertebrae and ribs (D)</p> Signup and view all the answers

    During week 4 of development, which significant event occurs related to the primitive heart tube?

    <p>It begins to beat, initiating blood circulation (C)</p> Signup and view all the answers

    What are the derivatives of the first pharyngeal arch?

    <p>Malleus and Incus (A), Maxilla and Mandible (B)</p> Signup and view all the answers

    Which cranial nerve supplies the muscles formed from the second pharyngeal arch?

    <p>Facial (CN VII) (D)</p> Signup and view all the answers

    What early development marks the initial formation of limb structures in week 4?

    <p>Appearance of limb buds (A)</p> Signup and view all the answers

    What is a primary function of the circulation initiated by the beating heart in week 4?

    <p>To provide nutrients and oxygen to tissues (C)</p> Signup and view all the answers

    Which of the following structures does NOT develop from the pharyngeal arches?

    <p>Vertebrae (C)</p> Signup and view all the answers

    Which muscle groups are primarily developed from the myotome component of the somite?

    <p>Epaxial and hypaxial muscles (D)</p> Signup and view all the answers

    Flashcards

    Neural Tube Formation

    The process of converting the neural plate, a flat sheet of ectoderm, into a hollow tube that will eventually become the brain and spinal cord.

    Neural Tube Closure

    The cranial end of the neural tube closes first, followed by the caudal end. This closure process is essential for the proper formation of the brain and spinal cord.

    Neural Crest Cells

    Cells that emerge from the neural tube folds and migrate to various parts of the embryo, forming the peripheral nervous system, parts of the face, and other structures.

    Spina Bifida

    A condition that results from the incomplete closure of the neural tube, leading to defects in the spinal cord and vertebrae.

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    Anencephaly

    A birth defect characterized by the absence of a major portion of the brain and skull.

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    Somites

    Blocks of mesoderm that develop alongside the neural tube during the fourth week of embryonic development.

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    Somite Differentiation

    The process by which somites contribute to the formation of the axial skeleton (vertebrae and ribs) and the skeletal musculature.

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    Primitive Heart Tube Formation

    The development of the heart, a complex organ that pumps blood throughout the body, beginning with the formation of the primitive heart tube.

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    What are somites?

    The mesodermal tissue that forms along the dorsal aspect of the developing embryo. Each somite will give rise to specific structures.

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    What does the sclerotome form?

    A part of the somite that forms the vertebrae, ribs, and intervertebral discs. It gives rise to the axial skeleton.

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    What does the dermatome form?

    A part of the somite that forms the dermis of the skin. It contributes to the segmented body regions.

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    What does the myotome form?

    A part of the somite that gives rise to skeletal muscles of the back, trunk, and limbs. It forms both the epaxial and hypaxial muscles.

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    What is the primitive heart tube?

    The first stage of heart development, where a single, linear tube begins to beat and pump blood.

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    What is looping of the heart tube?

    The process by which the primitive heart tube loops and folds to create the chambers of the heart. It is important for proper heart function.

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    What are pharyngeal arches?

    The paired structures in the developing embryo that give rise to various structures in the head and neck. They contribute to bones, muscles, and nerves.

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    What does the first pharyngeal arch form?

    The first pair of pharyngeal arches, which form the jaw, muscles of mastication, and some ear bones. They play a crucial role in facial development.

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    Study Notes

    Human Embryology - Week 4 Development

    • Learning Outcomes: Students will understand neural tube development, somite formation, heart development, pharyngeal arch formation, and limb bud development during week 4 of embryo development.

    Neurulation: Neural Tube Formation (Week 4)

    • Neural tube formation is critical for central nervous system (CNS) development.
    • The neural plate folds into a neural tube, forming brain and spinal cord.
    • Cranial closure begins at the head end of the tube.
    • Caudal closure occurs towards the tail end of the tube.
    • Neural crest cells form from neural tube folds, developing into peripheral nerves and facial bones.
    • Clinical Correlation: Problems with neurulation can lead to spina bifida and anencephaly.

    Somite Formation (Week 4)

    • 20-25 somites form during week 4, giving rise to various tissues and structures.
    • Somites are blocks of mesoderm alongside the neural tube.
    • They contribute to axial skeleton (vertebrae and ribs) and skeletal musculature.
    • Somites define the segmented body plan of the embryo.
    • Sclerotome: Forms vertebrae, ribs, and intervertebral discs (axial skeleton).
    • Dermatome: Forms the dermis of the skin (segmental body regions).
    • Myotome: Forms skeletal muscles of the back, trunk, and limbs (epaxial and hypaxial muscles)

    Heart Development (Week 4)

    • The primitive heart tube starts beating in week 4, initiating blood circulation.
    • The heart tube initially develops linearly but loops to form heart chambers.
    • Blood is pumped from the primitive heart to various parts of the embryo for nutrient and oxygen delivery.

    Pharyngeal Arches (Week 4)

    • The first two pairs of pharyngeal arches appear in week 4.

    • These arches eventually give rise to head and neck structures, including bones, muscles, and nerves.

    • 1st arch: Develops into maxilla, mandible, and muscles of mastication.

    • 2nd arch: Develops into stapes of ear and facial expression muscles.

    • Cartilage Derivatives: Malleus, Incus, Mandible, Ligaments

    • Muscle Derivatives: Mastication, Mylohyoid, Tensor, Facial Expression, Stapedius, Stylohyoid

    • Nerve Supply: Mandibular (CN V3), Facial (CN VII)

    • Arterial Derivatives: Maxillary, Stapedial, Hyoid

    • These arches form various head and neck tissues.

    Limb Bud Formation (Week 4)

    • Limb buds form in week 4, marking the start of limb development.
    • Upper limb buds appear slightly earlier than lower limb buds.
    • Limb buds are composed primarily of mesoderm, which develops into bones and muscles, and ectoderm, which develops into skin.
    • Limb buds elongate and differentiate into arms and legs, with fingers and toes developing later in embryonic development.

    Summary of Key Events (Week 4)

    • Neurulation forms brain and spinal cord.
    • Somites form axial skeleton and musculature.
    • Heart begins beating and blood circulation starts.
    • Pharyngeal arches form head and neck structures.
    • Limb buds initiate arm and leg development.

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    BIU Lesson 04 Week 4 Human Development PDF

    Description

    This quiz covers the crucial developments that occur during the fourth week of human embryology, including neural tube formation, somite development, and early heart formation. Understand the significance of these processes and their clinical correlations, like spina bifida and anencephaly.

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