Innervation of adult human laryngeal muscle fibers

• Published in: Journal of the neurological sciences 1997-07, Vol.149 (1), p.81-86
• Main Authors: Périé, Sophie, Lacau St Guily, Jean, Callard, Patrice, Sebille, Alain
• Format: Article
• Language: English
• Subjects: Adult; Aged; Aging; Aging - physiology; Axons - physiology; Axons - ultrastructure; Biological and medical sciences; Cholinesterase; Cholinesterases - analysis; Ear and associated structures. Auditory pathways and centers. Hearing. Vocal organ. Phonation. Sound production. Echolocation; Fundamental and applied biological sciences. Psychology; Human; Humans; Laryngeal muscles; Laryngeal Muscles - cytology; Laryngeal Muscles - innervation; Middle Aged; Motor Endplate - physiology; Motor Endplate - ultrastructure; Multi-innervation; Muscle Fibers, Skeletal - cytology; Muscle Fibers, Skeletal - physiology; Muscle Fibers, Skeletal - ultrastructure; Neuromuscular junction; Organ Specificity; Unineuronal innervation; Vertebrates: nervous system and sense organs
• ISSN: 0022-510X; 1878-5883
• DOI: 10.1016/S0022-510X(97)05395-1

The innervation of laryngeal muscle fibers was appraised in adult humans. Sixteen intrinsic laryngeal muscles were dissected during the autopsy of 4 adults (41–71 years old). Longitudinal serial frozen sections, 60 μm thick, of the whole muscles were double-stained for cholinesterase activity and axonal visualization. About 945 endplates per muscle were analysed using light microscopy. The neuromuscular junctions were always scattered throughout the whole muscles. Most of the muscle fibers showed a single neuromuscular junction, but multi-innervated fibers were found in all of the muscles. Their number was highest in interarytenoid muscles (21% of all the fibers). The distance between multiple neuromuscular junctions was most frequently less than 150 μm. Two neuromuscular junctions were frequently displayed, opposite one another, particularly in thyroarytenoid muscles, and this unusual feature seems specific for laryngeal muscles. The innervation of all of the muscle fibers was exclusively found to be unineuronal, with multi-innervated fibers being innervated by a single axon. Distal axonal degeneration occurred with aging, resulting in a loss in the number of multi-innervated muscle fibers.