Shrestha S, Basnet L M, Shakya S, Ghosh S K
Nepal Med Coll J. 2014 Dec;16(2-4):201-4.
Rectus Sternalis is a rare flat slip of muscle present parasternally in the thoracic wall. During the regular dissection of pectoral region, three slips of Sternalis muscle were observed bilaterally in an adult male cadaver. On the right side there was a single slip (RS 1) while on the left side two slips (RS2 and RS3) were present. All three slips were present anterior to the Pectoralis Major muscle of respective side and each muscle had fleshy origin and tendinous insertions. RS1 had two heads arising from the aponeurosis of External Oblique and Rectus Abdominis. RS2 had a single origin from aponeurosis of Rectus Abdominis and RS3 took its origin from the aponeurosis of Pectoralis Major muscle. Indistinct tendinous intersections were noted in both RS1 and RS3 slips proximal to fusion of both Sternalis muscle (RS1 and RS3) with each other. Out of three slips, right Rectus Sternalis was largest with breadth 3.8cm near its origin while the second slip of Rectus Sternalis on the left was longest with length of 12.5cm. RS2 was smallest and shortest among the three slips. The RS1 even presented a flattened tendon running upwards which fused with the membranous origin of right Sternocleidomastoid muscle. The Rectus Sternalis when present arises from hypomeres as longitudinal group of muscles which usually disappears in the thoracic region. The knowledge about Sternalis muscle and its variations is important for anatomists and clinicians (radiologists and surgeons) to avoid any confusion and misdiagnosis as well as anthropologists.
胸骨直肌是一种罕见的扁平肌束，位于胸壁胸骨旁。在对一名成年男性尸体的胸部区域进行常规解剖时，双侧观察到三块胸骨肌束。右侧有一块肌束（RS 1），而左侧有两块肌束（RS2和RS3）。所有三块肌束均位于各自一侧胸大肌的前方，每块肌肉都有肉质起点和腱性止点。RS1有两个头，分别起自腹外斜肌腱膜和腹直肌。RS2起自腹直肌腱膜，RS3起自胸大肌腱膜。在RS1和RS3肌束近端，两块胸骨肌（RS1和RS3）相互融合处可见不明显的腱划。在这三块肌束中，右侧胸骨直肌最大，起点处宽度为3.8厘米，而左侧第二块胸骨直肌最长，长度为12.5厘米。RS2在三块肌束中最小且最短。RS1甚至有一条向上走行的扁平肌腱，与右侧胸锁乳突肌的膜性起点融合。胸骨直肌若存在，则起自下肌节，为纵向肌组，通常在胸部区域消失。了解胸骨肌及其变异情况对于解剖学家、临床医生（放射科医生和外科医生）以及人类学家避免任何混淆和误诊非常重要。
