M Line

M-line - Refers to a dark line through the middle of a sacromere, bisecting the two halves between Z disks when viewed under a microscope.  The M-band is composed of proteins myomesin, C-protein, the M-line portion, as well as other cross-links between the thick filament system (myosin). Example, Just as the Z disk anchors actin filaments, the M-line aids in anchoring myosin filaments.
  1. Saladin, K. (2014). Anatomy & physiology: The unity of form and function. McGraw-Hill Higher Education, New York. ISBN: 9780073403717

Related Terms

  • sarcomere
  • actin filaments
  • myosin filaments
  • Z-disk
  • myomesin
  • C-protein


  • M line
  • Mittelscheibe
  • M band