INTERNAL ORGANIZATION IN THE HUMAN JAW MUSCLES
INTERNAL ORGANIZATION IN THE HUMAN JAW MUSCLES
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DOI：
10.1177/10454411940050010301
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发表时间：
1994-01-01
期刊：
影响因子：
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通讯作者：
MCMILLAN, AS
中科院分区：
文献类型：
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作者：
HANNAM, AG;MCMILLAN, AS
人类下颌肌肉对于咀嚼至关重要，并且在颅面生长中发挥重要作用。 它们会产生牙齿和关节力，使下颌骨变形，并且与其他组织一样，容易出现疾病，通常表现为疼痛。 文献描述了它们的收缩如何由神经系统控制，以及它们的一般结构和功能如何对颅面生物学做出贡献，但对其内部组织的评估很少。 这些肌肉大部分都不简单；它们是多羽状的，层状复杂，并被腱膜分开。 这种布置为差异收缩提供了实质手段。 在许多方面，颌肌纤维本质上与其他骨骼肌中发现的肌纤维不同，因为它们排列成均匀的簇，并且通常显示 I 型或 II 型组织化学特征。 大多数为 I 型，优先分布在颌闭合器的前部和更深部。 此外，大多数运动单位 (MU) 区域都小于四肢的区域。 有间接证据表明肌内分区部分基于初级肌肉神经分支的神经支配。 在正常功能期间，人类下颌肌肉中的 MU 募集和 MU 发射速率编码遵循为四肢建立的一般原则，但即使在这里，它们在重要方面也有所不同。 下颌肌肉 MU 没有稳定的力量募集阈值，并且似乎更多地依赖于速率编码而不是顺序单位募集来对肌肉收缩的幅度进行分级。 与四肢不同，它们的抽搐张力与 MU 疲劳性和收缩速度相关性较弱，可能是因为下颌肌肉中缓慢、抗疲劳的 MU 很少。 此外，如此大量存在的 I 型纤维的收缩速度并不像通常预期的那么慢。 使问题变得复杂的是，估计下颌 MU 抽搐张力极其困难，因为它受到用于测量抽搐的位置、背景放电率、肌肉共激活以及区域肌内力学的影响。 最后，关于下颌 MU 反射行为的系统研究很少。 最近的研究集中于外感受抑制，并表明口内和口周刺激后的 MU 抑制取决于 MU 的位置、其背景放电率、刺激的时间以及用于驱动该单元的任务。 任务依赖性是人类下颌 MU 行为的一个共同特征，反映了来自口面部和肌肉传入的外周感觉信息与皮质延髓驱动之间的相互作用。 总之，包括肌内结构、内在 MU 的配置和生理行为在内的几条证据强烈表明，人类下颌肌肉的内部组织是独特的。 结构和功能属性都需要纳入每块肌肉的假设模型中，以便解释其在正常使用过程中如何产生局部张力和位移，以及可能在其中诱发任何无序生物力学事件的情况。
The human jaw muscles are essential to mastication and play an important part in craniofacial growth. They contribute to dental and articular forces, deform the mandible, and, like other tissues, are subject to disorders, often manifested as pain. The literature describes how their contraction is controlled by the nervous system, and how their general structure and function contribute to craniofacial biology, but there has been little appraisal of their internal organization. Most of these muscles are not simple; they are multipennate, complexly layered, and divided by aponeuroses. This arrangement provides substantial means for differential contraction. In many ways, jaw muscle fibers are intrinsically dissimilar from those found in other skeletal muscles, because they are arranged in homogeneous clusters and generally reveal type I or type II histochemical profiles. Most are type I and are distributed preferentially in the anterior and deeper parts of the jaw closers. Additionally, most motor unit (MU) territories are smaller than those in the limbs. There is circumstantial evidence for intramuscular partitioning based in part on innervation by primary muscle nerve branches. During normal function, MU recruitment and the rate coding of MU firing in human jaw muscles follow the general principles established for the limbs, but even here they differ in important respects. Jaw muscle MUs do not have stable force recruitment thresholds and seem to rely more on rate coding than on sequential unit recruitment to grade the amplitude of muscle contraction. Unlike those in the limbs, their twitch tensions correlate weakly with MU fatiguability and contraction speed, probably because there are so few slow, fatigue-resistant MUs in the jaw muscles. Moreover, the type I fibers that are present in such large numbers do not contract as slowly as normally expected. To complicate matters, estimation of jaw MU twitch tensions is extremely difficult, because it is affected by the location used to measure the twitch, the background firing rate, muscle coactivation, and regional, intramuscular mechanics. Finally, there have been very few systematic studies of jaw MU reflex behavior. The most recent have concentrated on exteroceptive suppression and suggest that MU inhibition following intra- and perioral stimulation depends on the location of the MU, its background firing rate, the timing of the stimulus, and the task used to drive the unit. Task dependency is a common feature of human jaw MU behavior, reflecting interaction between peripheral sensory information from orofacial and muscle afferents and corticobulbar drive. In summary, several lines of evidence, including intamuscular structure, the disposition and physiological behavior of the intrinsic MUs, strongly suggest that human jaw muscles are uniquely organized internally. Both structural and functional attributes need to be incorporated into a hypothetical model of each muscle in order to explain how it produces local tensions and displacements during normal use and the circumstances under which any disordered biomechanical events might be induced in it.