Myofibrils and Heart Conduction System
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Questions and Answers

What role does Bone morphogenetic protein 4 (BMP4) play in muscle development?

  • It is involved in the formation of muscle vascularization.
  • It signals dermomyotome cells to produce MyoD. (correct)
  • It directly stimulates muscle contraction.
  • It provides nutritional support for muscle cells.
  • Which proteins are secreted by the notochord and floor plate of the neural tube during muscle development?

  • WNT proteins
  • Sonic hedgehog (SHH) proteins (correct)
  • Fibroblast growth factors
  • BMP4 proteins
  • Which cells are indicated to be influenced by WNT proteins from the dorsal neural tube?

  • Abaxial muscle cells
  • Ventral dermomyotome cells
  • VLL cells of the dermomyotome (correct)
  • Primaxial muscle cells
  • In the context of muscle development, what distinguishes primaxial domains from abaxial domains?

    <p>Primaxial domains derive from the dermomyotome.</p> Signup and view all the answers

    What is the difference between epimeres and hypomeres in muscle classification?

    <p>Epimeres correspond to axial muscles, while hypomeres correspond to limb and body wall muscles.</p> Signup and view all the answers

    What is a characteristic feature of Poland sequence?

    <p>Absence or displacement of nipple and areola</p> Signup and view all the answers

    Poland sequence is primarily attributed to which type of tissue development?

    <p>Connective tissue derived from parietal layer of lateral plate mesoderm</p> Signup and view all the answers

    What unusual digital defects may occur in individuals with Poland sequence?

    <p>Syndactyly - fused digits</p> Signup and view all the answers

    Cardiac muscle myofibrils share similarities with which type of muscle?

    <p>Skeletal muscle, but will not fuse</p> Signup and view all the answers

    What component facilitates the adherence of myoblasts in developing cardiac muscle?

    <p>Intercalated discs</p> Signup and view all the answers

    Which of the following statements about Poland sequence is FALSE?

    <p>It involves complete absence of pectoralis major muscle</p> Signup and view all the answers

    The muscles in the head and neck during the embryonic stage are derived from which source?

    <p>Somitomeres and myotomes</p> Signup and view all the answers

    What is the result of cardiac muscle development from splanchnic mesoderm?

    <p>Development of specialized cardiac structures</p> Signup and view all the answers

    Which type of muscle is derived from the splanchnic layer of lateral plate mesoderm?

    <p>Smooth muscle</p> Signup and view all the answers

    Which transcription factor is primarily responsible for smooth muscle differentiation?

    <p>Serum Response Factor (SRF)</p> Signup and view all the answers

    What role do Myocardin and MRTFs play in smooth muscle development?

    <p>They enhance the activity of SRF.</p> Signup and view all the answers

    From where does the mesenchyme that contributes to limb musculature originate?

    <p>Dorsolateral cells of the somites</p> Signup and view all the answers

    When is the first indication of limb musculature observed during development?

    <p>Week seven</p> Signup and view all the answers

    What initiates the genetic cascade responsible for smooth muscle development?

    <p>Growth factors and SRF</p> Signup and view all the answers

    What is NOT a derived structure from the ectoderm?

    <p>Smooth muscle in the gut wall</p> Signup and view all the answers

    Which somite group contributes to the development of the craniofacial muscles?

    <p>Somites 2 to 5</p> Signup and view all the answers

    What comprises the abaxial muscle cell precursors?

    <p>Muscle cells that cross the lateral somitic frontier into the lateral plate mesoderm</p> Signup and view all the answers

    Which cells are primarily responsible for forming tendons during muscle development?

    <p>Scleraxis - transcription factor</p> Signup and view all the answers

    Which region do the VLL cells migrate to in muscle development?

    <p>Into the parietal layer of lateral plate mesoderm</p> Signup and view all the answers

    What is formed from cells at the DML and VLL regions of the somite?

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

    What differentiates the primaxial mesodermal domain from the abaxial mesodermal domain?

    <p>It only comprises somitic cells</p> Signup and view all the answers

    From where do primaxial muscle cell precursors primarily receive their developmental signals?

    <p>From the neural tube and notochord</p> Signup and view all the answers

    What do somite-derived cells contribute to in the context of muscle cell formation?

    <p>The abaxial mesodermal domain</p> Signup and view all the answers

    What is the primary origin of muscle cell precursors in the ventral region ventral to the dermatome?

    <p>Cells from the dermomyotome</p> Signup and view all the answers

    What is a characteristic feature of Prune Belly Syndrome?

    <p>Visible organs due to thin abdominal wall</p> Signup and view all the answers

    Which embryonic origin is responsible for smooth muscle in coronary arteries?

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

    Which signal induces VIL in the development of smooth muscle?

    <p>WNT from lateral plate mesoderm</p> Signup and view all the answers

    What type of musculature is affected in Prune Belly Syndrome?

    <p>Smooth abdominal musculature</p> Signup and view all the answers

    What causes the accumulation of fluid in the abdomen associated with Prune Belly Syndrome?

    <p>Urethral obstruction</p> Signup and view all the answers

    What does the connective tissue generate in muscle pattern establishment?

    <p>Muscle pattern templates</p> Signup and view all the answers

    Which signals from the notochord induce DML cells?

    <p>SHH and WNT</p> Signup and view all the answers

    From which embryonic layer are the smooth muscles of the dorsal aorta and large arteries derived?

    <p>Lateral plate mesoderm and neural crest cells</p> Signup and view all the answers

    Study Notes

    Myofibril Formation and Muscle Development

    • Distributed myofibrils emerge during later stages of muscular development.
    • Cardiac conduction fibers originate from specialized muscle cells crucial for heart function.
    • Smooth muscle in large arteries and the dorsal aorta develops from lateral plate mesoderm and neural crest cells.

    Prune Belly Syndrome

    • Characterized by partial or complete absence of abdominal muscles, leading to visible and palpable organs.
    • Common malformations include urinary tract defects and bladder issues, such as urethral obstruction.
    • This condition can result in fluid accumulation in the abdomen, causing muscle atrophy.

    Poland Sequence

    • Occurs in approximately 1 in 20,000 individuals.
    • Noted for the absence of the pectoralis minor muscle and partial loss of the pectoralis major, specifically the sternal head.
    • Accompanying symptoms may include nipple and areola displacement and digital defects such as syndactyly and brachydactyly.

    Cardiac Muscle Development

    • Cardiac muscle arises from splanchnic mesoderm around the endothelial heart tube.
    • Myoblasts form intercalated discs through cell adhesion, essential for cardiac function.
    • Purkinje fibers, unique muscle cell bundles, develop from remaining embryonic muscle cells.

    Dermomyotome and Muscle Patterning

    • Dermomyotome is derived from the combination of ventrolateral (VLL) and dorsomedial (DML) cells.
    • Abaxial muscle cell precursors migrate into lateral plate mesoderm, influenced by signals from the neural tube and notochord.
    • Primaxial muscle cells remain in the paraxial mesoderm, relying on locally sourced developmental signals.

    Molecular Regulation of Muscle Development

    • Bone morphogenetic protein 4 (BMP4) and fibroblast growth factors guide differentiation in muscle cells.
    • WNT proteins stimulate VLL cells to express muscle-specific gene MyoD, vital for muscle development.
    • Sonic hedgehog (SHH) signaling from the notochord also impacts the DML cells for muscle patterning.

    Innervation of Axial Skeletal Muscles

    • Each myotome is innervated by spinal nerves from the same segment, ensuring coordinated function.
    • New classification of muscle development splits muscles into primaxial (back) and abaxial (limb) domains, replacing older definitions based on innervation styles.

    Smooth Muscle Sources

    • Smooth muscle in the gut wall and related organs arises from the splanchnic layer of lateral plate mesoderm.
    • Sphincter muscles, pupil muscles, and glandular tissues come from ectoderm.
    • Serum Response Factor (SRF) is crucial for smooth muscle differentiation, influenced by growth factors and signaling pathways.

    Limb Musculature

    • Initial limb musculature appears in week 7 of embryonic development as mesenchymal condensation.
    • This mesenchyme originates from dorsolateral somite cells that migrate to limb buds to establish the muscular framework.

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    Description

    Explore the development of myofibrils and their role in the heart's conduction system. Learn about Prune Belly Syndrome, which is characterized by a lack of abdominal musculature. This quiz covers the importance of these physiological concepts in human anatomy.

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