Origin: trunk - paraxial mesoderm, somites, myotomes; limbs - mesenchyme; eye - neuromesenchyme.
(multinucleated syncytium, symplasts)
Function: contraction: movements and maintenance of body position, posture.
Composition: contractile proteins: actin, myosin, tropomyosin, troponin and others; myoglobin, glycogen, calcium ions...
Composition: large amounts of myoglobin and cytochromes, oxidative enzymes, ATP-ase of slow type.
Composition: large amounts of glycogen, glycolitic enzymes, ATP-ase of fast type.
Composition: between red and white fibers.
Function: stem cells, may proliferate.
Location: between plasma membrane and basal lamina of fiber.