Cardiac, and Smooth Muscle

Cardiac Muscle

  • Origin: Lateral mesoderm moving into the splanchnic mesoderm.
  • Structure:
    • Composed of individual cells joined end to end, unlike the syncytial fibers of skeletal muscle.
    • Cells are branched.
    • Striated with a centrally located nucleus.
    • Joined at intercalated discs.
  • Development:
    • Precardiac mesoderm cells coalesce to form heart muscle.
    • Myocytes form in the wall of the cardiac tube.
    • Cells divide (mitosis) in place as the heart grows.
    • Cells disassemble contractile filaments, undergo myatosis, and renew connections.

Smooth Muscle

  • Origin: Lateral mesoderm (splanchnic mesoderm) and local mesoderm for mesenchymal cells.
  • Location: Lining hollow tubes/organs, often associated with epithelium (e.g., esophagus, bladder, vas deferens, bronchus, arteries, aorta, sweat glands, uterine wall).
  • Types:
    • Multiunit:
      • Found in walls of blood vessels.
      • Derived from local mesenchyme.
      • Functionally independent, innervated by single nerve termini.
      • Do not contract simultaneously, allowing for localized control of blood flow.
    • Visceral:
      • Bundles of smooth muscle cells connected by gap junctions.
      • Contract simultaneously, such as in the walls of intestines.
      • Derived from lateral mesoderm (splanchnic mesoderm).
  • Proliferative Capacity:
    • Significant capacity to regenerate and multiply, especially in the uterine wall during pregnancy.
    • Develops by individual mesodermal cell differentiation.
    • Can expand significantly, as seen in the growth of the uterus during pregnancy.

Regenerative Abilities of Muscle Types

  • Smooth Muscle: Best regenerative ability.
    • Cells can be proliferative and can differentiate and proliferate simultaneously to support wound healing.
    • Can grow in both numbers and size.
  • Skeletal Muscle: Intermediate regenerative ability.
    • Satellite cells aid in regeneration and repair.
  • Cardiac Muscle: Poor regenerative ability, especially in humans.

Zebrafish Model for Cardiac Regeneration

  • Zebrafish have an exceptional ability to regenerate heart muscle after damage.
  • Research on zebrafish aims to understand and potentially apply their regenerative mechanisms to improve cardiac repair in humans.

Summary of Muscle Types:

  • Skeletal Muscle:
    • Multinucleated.
    • Long cylindrical cells.
    • Striations.
    • Peripheral nuclei.
  • Cardiac Muscle:
    • Intercalated discs.
    • Branching structures.
    • Central nuclei.
    • Striations.
  • Smooth Muscle:
    • No Striations.
    • Centrally located single nuclei.