title: Ultrastructure of nerve endings in the stapedius muscle of the squirrel monkey.
abstract: The stapedius muscle of the squirrel monkey (Saimiri sciureus) was studied electron microscopically with regard to neuromuscular junctions, muscle-tendon junctions and tendons. Two types of neuromuscular junctions were identified. The first type which was predominant in number showed well-developed primary and secondary synaptic clefts. They were almost the same with those of other mammalian skeletal muscles. The second type showed a flat-shaped junction with fewer secondary synaptic clefts. Muscle-tendon junctions were characterized by many interdigitations between the muscle fibers and tendon. The tendon was composed of collagen fibers, approximately 70-100 nm in diameter. Muscle spindles were not present, while nerve endings resembling the Golgi tendon organ were found adjacent to the tendon and the muscle-tendon junctions. These findings suggest that a feedback system may exist and regulate the fine contractile function of this muscle.
authors.affiliation: Department of Otolaryngology, Tokyo Women's Medical College, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Yoshihara
authors.forename: H
authors.initials: H
authors.lastname: Kaname
authors.forename: T
authors.initials: T
authors.lastname: Ishii
authors.forename: M
authors.initials: M
authors.lastname: Igarashi
mesh_terms: D000818:Animals; D006801:Humans; D008854:Microscopy, Electron; D009469:Neuromuscular Junction / Q000648:ultrastructure*; D012453:Saimiri; D013198:Stapedius / Q000294:innervation / Q000648:ultrastructure*; D013710:Tendons / Q000648:ultrastructure*