Padova Neuroscience Center, University of Padova, 35129 Padova, Italy.
Institute of Human Anatomy, Department of Neuroscience, University of Padova, 35122 Padova, Italy.
Int J Mol Sci. 2024 Jul 3;25(13):7320. doi: 10.3390/ijms25137320.
Muscle spindles have unique anatomical characteristics that can be directly affected by the surrounding tissues under physiological and pathological conditions. Understanding their spatial distribution and density in different muscles is imperative to unravel the complexity of motor function. In the present study, the distribution and number/density of muscle spindles in human and animal muscles were reviewed. We identified 56 articles focusing on muscle spindle distribution; 13 articles focused on human muscles and 43 focused on animal muscles. The results demonstrate that spindles are located at the nerve entry points and along distributed vessels and they relate to the intramuscular connective tissue. Muscles' deep layers and middle segments are the main topographic distribution areas. Eleven articles on humans and thirty-three articles on animals (totaling forty-four articles) focusing on muscle spindle quantity and density were identified. Hand and head muscles, such as the pronator teres/medial pterygoid muscle/masseter/flexor digitorum, were most commonly studied in the human studies. For animals, whole-body musculature was studied. The present study summarized the spindle quantity in 77 human and 189 animal muscles. We identified well-studied muscles and any as-yet unfound data. The current data fail to clarify the relationship between quantity/density and muscle characteristics. The intricate distribution of the muscle spindles and their density and quantity throughout the body present some unique patterns or correlations, according to the current data. However, it remains unclear whether muscles with fine motor control have more muscle spindles since the study standards are inconsistent and data on numerous muscles are missing. This study provides a comprehensive and exhaustive approach for clinicians and researchers to determine muscle spindle status.
肌梭具有独特的解剖学特征，在生理和病理条件下可直接受到周围组织的影响。了解不同肌肉中肌梭的空间分布和密度对于揭示运动功能的复杂性至关重要。在本研究中，回顾了人类和动物肌肉中肌梭的分布和数量/密度。我们确定了 56 篇聚焦于肌梭分布的文章；13 篇聚焦于人类肌肉，43 篇聚焦于动物肌肉。结果表明，肌梭位于神经进入点和分布的血管附近，与肌内结缔组织有关。肌肉的深层和中段是主要的拓扑分布区域。有 11 篇关于人类和 33 篇关于动物（共 44 篇）的文章聚焦于肌梭的数量和密度。人类研究中最常研究手部和头部肌肉，如旋前肌/翼内肌/咬肌/指深屈肌。对于动物，研究了全身肌肉。本研究总结了 77 个人类和 189 个动物肌肉中的肌梭数量。我们确定了研究较多的肌肉和任何尚未发现的数据。目前的数据无法阐明数量/密度与肌肉特征之间的关系。根据目前的数据，肌梭在全身的复杂分布及其密度和数量呈现出一些独特的模式或相关性。然而，由于研究标准不一致且许多肌肉的数据缺失，尚不清楚具有精细运动控制的肌肉是否具有更多的肌梭。本研究为临床医生和研究人员提供了一种全面详尽的方法来确定肌梭的状态。
