week 7!

• Developmental origins of muscle
• Gastrulation and initial mesoderm formation

  1. Mesoderm differentiation

  2. Paraxial

  3. Intermediate

  4. Chordamesoderm

  5. Lateral plate mesoderm
• Skeletal muscle


  • Develops from fusion of myoblasts
  • Long fibres, multinucleated (peripheral nuclei) fused cells
  • Evident striations
• Cardiac muscle


  • Develops by end-to-end joining of cardiomyoblasts
  • Intercalated discs form between adjacent cells
  • Single, centrally placed nucleus
  • Striations and branching evident
• Smooth muscle


  • Develops by individual mesodermal cell differentiation
  • Spindle-shaped cells – NO striations evident
  • Single, centrally placed nucleus
• Skeletal, cardiac and smooth muscles all working together
• Muscle types have differing capacity to repair and regenerate. Smooth muscle has the highest regenerative capacity, followed by skeletal muscle, and cardiac muscle has the lowest regenerative capacity.
• Cardiac and skeletal muscle cells undergo terminal differentiation, retaining their phenotype in adult organs

  
• Smooth muscle cells are highly versatile and can change their phenotype, being proliferative in growing organs like the pregnant uterus, and differentiating and proliferating at the same time in wound healing of blood vessels
• Smooth muscle growth can occur through hyperplasia (increase in cell numbers) and hypertrophy (increase in cell size)