Department of Biological Sciences, North Carolina State University, Raleigh, North Carolina.
University of South Carolina School of Medicine, Columbia, South Carolina.
Anat Rec (Hoboken). 2020 May;303(5):1364-1373. doi: 10.1002/ar.24259. Epub 2019 Oct 6.
The masticatory apparatus has been the focus of many studies in comparative anatomy-especially analyses of skulls and teeth, but also of the mandibular adductor muscles which are responsible for the production of bite force and the movements of the mandible during food processing and transport. The fiber architecture of these muscles has been correlated to specific diets (e.g., prey size in felids) and modes of foraging (e.g., tree gouging in marmosets). Despite the well-elucidated functional implications of this architecture, little is known about its ontogeny. To characterize age-related myological changes, we studied the masticatory muscles in a large (n = 33) intraspecific sample of a small, Malagasy primate, Microcebus murinus including neonatal through geriatric individuals. We removed each of the mandibular adductors and recorded its mass as well as other linear measurements. We then chemically dissected each muscle to study its architecture-fascicle length and physiological cross-sectional area (PCSA) which relate to stretch (gape) and force capabilities, respectively. We observed PCSA and muscle mass to increase rapidly and plateau in adulthood through senescence. Fascicle lengths remained relatively constant once maximal length was reached, which occurred early in life, suggesting that subsequent changes in PCSA are driven by changes in muscle mass. Quadratic curvilinear models of each of the architectural variables of all adductors combined as well as individual muscles regressed against age were all significant. Anat Rec, 303:1364-1373, 2020. © 2019 American Association for Anatomy.
咀嚼器官一直是比较解剖学的研究焦点——尤其是对头骨和牙齿的分析，但也包括负责产生咬合力和在食物加工和运输过程中下颌运动的下颌内收肌。这些肌肉的纤维结构与特定的饮食（例如，猫科动物的猎物大小）和觅食方式（例如，狨猴的树洞挖掘）有关。尽管这种结构的功能意义已经得到了很好的阐明，但对其发育知之甚少。为了描述与年龄相关的肌肉变化，我们对马达加斯加小型灵长类动物 Microcebus murinus 的一个大型（n=33）种内样本的咀嚼肌进行了研究，包括新生儿到老年个体。我们取出每块下颌内收肌并记录其质量以及其他线性测量值。然后，我们通过化学方法对每块肌肉进行解剖，以研究其结构——肌束长度和生理横截面积（PCSA），分别与伸展（张口）和力的产生能力有关。我们观察到 PCSA 和肌肉质量在成年后迅速增加并达到平台期，直到衰老。一旦达到最大长度，肌束长度就会保持相对稳定，这发生在生命早期，这表明随后 PCSA 的变化是由肌肉质量的变化驱动的。所有内收肌的结构变量以及单个肌肉的二次曲线模型与年龄的回归都是显著的。解剖学记录，303：1364-1373，2020。© 2019 美国解剖学会。
