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Glossary Term

M Line

The M-line is a vital structure in muscle physiology, forming a dark line down the center of the sarcomere. Composed of proteins including myomesin and C-protein, the M-line serves as an anchor point for myosin filaments during muscle contraction. This structure also helps maintain the structural integrity of the sarcomere, ensuring proper muscle function. Understanding the M-line is critical for grasping the mechanics of muscle contraction and the complex interplay between actin and myosin filaments.

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). For 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