Key result
Human laryngeal muscles contain more type I fibers than corresponding animal muscles.
Why the study?
The actomyosin ATPase activity and fiber type composition of human laryngeal muscles were examined to understand their characteristics compared to animal muscles.
Cross-Sectional (n=7)
Human laryngeal muscles possess a higher percentage of type I (slow-twitch) fibers compared to animals, which may be an evolutionary adaptation related to the development of speech.
Human laryngeal fiber composition may reflect speech adaptation; leaves open relevance to laryngology practice or animal model validity.
The muscles from seven human larynxes removed by laryngectomy have been examined for actomyosin ATPase by histochemical methods. The various muscles contained a mixture of ATPase low (type I) and ATPase high (type II) muscle fibres. The thyreoarytenoid muscle had the highest proportion of type II fibres (65%) and the posterior cricoarytenoid muscle had the highest proportion of type I fibres (67%). The other laryngeal muscles had intermediate valves. All human laryngeal muscles had a higher percetage of type I fibres than the corresponding muscles in animals so far examined, a finding which may be related to the development of speech.
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Teig et al. (1978) conducted a cross-sectional in Laryngectomy (n=7). Histochemical examination of actomyosin ATPase vs. Animal laryngeal muscles was evaluated on Proportion of type I and type II muscle fibres in various laryngeal muscles. Human laryngeal muscles contained a mixture of ATPase low and high fibres, with a higher percentage of type I fibres than corresponding animal muscles.
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