Toshiaki Masegi

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.

Muscle Spindle Distribution in the Masticatory Muscle of the Japanese Shrew-Mole

This investigation was designed to obtain anatomical information about the neuromuscular mechanism of human jaw movement by a comparative study of insectivores. Study of the masticatory muscles of the Japanese shrew-mole showed that muscle spindles are concentrated in restricted areas of the inner layer of the horizontal and vertical portions of the temporal muscle, the medial portion of the medial pterygoid muscle, and the deep portion of the masseter muscle. The lateral pterygoid muscle contains no spindles.

Muscle Spindle Distribution in the Masticatory Muscle of the Tree Shrew

Histological study of the masticatory muscles of the tree shrew showed that 140 muscle spindles are concentrated in the restricted areas of the inner lowermost layer of the horizontal and vertical portions of the temporal muscle (48 and 47 spindles, respectively), the profundus portion of the masseter muscle (42 spindles), and the zygomaticomandibular muscle (3 spindles). The medial and lateral pterygoid muscles are devoid of spindles.

Proprioceptive Innervation of the Masticatory Muscles in Pinché

This study of the masticatory muscles of the primate showed that the temporal muscle contained 107 muscle spindles, 45 in the horizontal portion and 62 in the vertical portion; the masseter muscle contained 70, 58 in the profundus portion and 12 in the superficial portion; the medial pterygoid muscle contained 15; the lateral pterygoid muscle contained 6; and the zygomaticomandibular muscle contained 9. The muscle spindles were located around the coronoid process and mandibular ramus.

Location of proprioceptive neurons innervating the muscle spindles of the snout muscles in the talpoides

Abstract Location of the primary neurons of the proprioceptive afferents from the facial musculature has been investigated by denervating the facial nerve in the Japanese shrew-mole and Japanese lesser shrew-mole. In all the cases at 5, 7 and 14 days after the operation, the muscle spindle innervation, the cells of the posterolateral group in the glossopharyngeal-vagus ganglion and the facial motor neurons on the treated side showed clearcut anterograde and retrograde changes, complete damage of the spindle nerve fibers, central chromatolysis and peripheral concentration of the Nissl granules and the excentric displacement of the nucleus in the cytoplasm of the neurons, justifying their classification as pathologically altered specimens. These findings are taken to provide experimental support for the demonstration that primary neurons of the proprioceptive afferents from the facial muscles of the talpoides exist in the posterolateral group of the glossopharyngeal-vagus ganglion. Also the presence of the thick ramus communicans between the facial nerve and the posterolateral part of the ganglion gives further information concerning the site of their somata in this part of the ganglion.