Muscle spindle supply to the human jaw muscle.

Histological study of the human jaw muscle revealed that the temporal muscle displayed 342 muscle spindles, 208 in the horizontal and 134 in the vertical portion; the masseter muscle contained 114 spindles, 91 in the superficial and 23 in the profound portion; the medial pterygoid muscle had 59; and the lateral pterygoid muscle contained 6, four in the upper head and two in the lower head. These data suggest that the extensive mobility of the temporomandibular joint, and the maintenance of mandibular posture during mastication and speech are strongly influenced by proprioceptive mechanisms.