Division of Anatomy, Faculty of Dentistry, "Carol Davila" University of Medicine and Pharmacy, Bucharest, Romania.
Department of Cellular and Molecular Biology, National Institute of Research and Development for Biological Sciences, Bucharest, Romania.
Ann Anat. 2023 Aug;249:152096. doi: 10.1016/j.aanat.2023.152096. Epub 2023 Apr 1.
The force a muscle exerts is partly determined by anatomical parameters, such as its physiological cross-section. The temporal muscle is structurally heterogeneous. To the authors' knowledge, the ultrastructure of this muscle has been poorly specifically studied.
Five adult Wistar rats weighting 350-400 g were used as temporal muscle donors. Tissues were specifically processed and studied under transmission electron microscope.
On ultrathin cuts, the general ultrastructural pattern of striated muscles was observed. Moreover, pennate sarcomeres were identified, sharing a one-end insertion on the same Z-disc. Bipennate morphologies resulted when two neighbor sarcomeres, attached on different neighbor Z-discs and separated at that end by a triad, converged to the same Z-disc at the opposite ends, thus building a thicker myofibril distinctively flanked by triads. Tripennate morphologies were identified when sarcomeres from three different Z-discs converged to the same Z-disc at the opposite ends.
These results support recent evidence of sarcomeres branching gathered in mice. Adequate identification of the sites of excitation-contraction coupling should be on both sides of a myofibril, on bidimensional ultrathin cuts, to avoid false positive results due to putative longitudinal folds of myofibrils.
肌肉产生的力部分取决于解剖学参数，例如其生理横截面积。颞肌在结构上是不均匀的。据作者所知，该肌肉的超微结构尚未得到充分研究。
使用 5 只体重 350-400g 的成年 Wistar 大鼠作为颞肌供体。组织经特殊处理后，在透射电子显微镜下进行研究。
在超薄切片上，观察到横纹肌的一般超微结构模式。此外，还鉴定出了羽状的肌节，它们在同一 Z 盘的一端插入。当两个相邻的肌节附着在不同的 Z 盘上，并在该端由三联体分开时，双羽状形态会汇聚到同一 Z 盘的相对端，从而形成一个明显由三联体包围的更厚的肌原纤维。当来自三个不同 Z 盘的肌节在相对端汇聚到同一 Z 盘时，会出现三羽状形态。
这些结果支持了在小鼠中收集到的关于肌节分支的最新证据。在二维超薄切片上，兴奋-收缩耦联的部位应该在肌原纤维的两侧，以避免由于肌原纤维的假定纵向折叠而产生假阳性结果。
