title: Density of muscle spindles in the jaw muscles of the Japanese flying squirrel and the guinea pig.
abstract: The number of muscle spindles and their distribution pattern in the jaw muscles were examined in serial sections of the heads of the Japanese flying squirrel and the guinea pig, and were compared with each other. The Japanese flying squirrel had 127 to 177 spindles, the length of which ranged from 140 microns to 1400 microns; 74 to 99 in the masseter, 39 to 47 in the temporalis, 11 to 28 in the zygomaticomandibularis, zero to one in the maxillomandibularis and two to three in the medial pterygoid muscles. The guinea pig had 322 to 346 spindles, the length of which ranged from 140 microns to 2800 microns; 116 to 125 in the masseter, 15 to 16 in the temporalis, 98 to 107 in the zygomaticomandibularis, 89 to 94 in the maxillomandibularis, and three to five in the medial pterygoid muscles. The lateral pterygoid, mylohyoid and anterior digastric muscles were devoid of spindles, as was the case in the other rodent species examined.
authors.affiliation: Department of Neurobiologie, Graduate School, Tokyo Medical and Dental University, Japan.
authors.forename: N
authors.initials: N
authors.lastname: Odagiri
authors.forename: K
authors.initials: K
authors.lastname: Kubota
authors.forename: S
authors.initials: S
authors.lastname: Shibanai
mesh_terms: D000818:Animals; D006168:Guinea Pigs / Q000033:anatomy & histology*; D008406:Masseter Muscle / Q000033:anatomy & histology / Q000166:cytology; D008410:Masticatory Muscles / Q000033:anatomy & histology*; D011626:Pterygoid Muscles / Q000033:anatomy & histology; D012589:Sciuridae / Q000033:anatomy & histology*; D013045:Species Specificity; D013704:Temporomandibular Joint / Q000033:anatomy & histology