Multiple Muscular Variations in the Neck, Upper Extremity, and Lower Extremity Biased toward the Left Side of a Single Cadaver

Abstract

Although numerous reports have found accessory or supernumerary muscles throughout the human body, multiple appearances of these variations biased toward one side of body are rare. We report a 76-yr-old male cadaver with an accessory head of the biceps brachii and palmaris profundus, and a muscular slip between the biceps femoris and semitendinosus on the left side in addition to a bilateral accessory belly of the digastric muscle. No remarkable nervous, vascular, or visceral variation accompanied these variations. An interruption of normal somitogenesis or myogenesis may be a cause of these variations.

An Anomalous Muscular Bundle Connecting Biceps Femoris to Semitendinosus

“…The aberrant muscular bundle in their report described an origin from 12 cm below the ischial tuberosity that joined the long head of biceps femoris at 12.5 cm above the medial epicondyle. More recently, Bang et al [12] reported a similar muscular bundle between the long head of the biceps femoris and semitendinosus muscles. The muscular bundle in their report originated from the long head of the biceps femoris, which was approximately 127.7 mm lower than was the ischial tuberosity and merged with the semitendinosus 110.5 mm above its insertion; its length was 138.8 mm.…”

A Possible Accessory Muscle of the Serratus Posterior Superior Muscle

“…In the present case, muscular variation biased toward the left side of the body suggests a disturbance during development may have affected the symmetry of the musculoskeletal system. In a recent study by Bang et al, 2015, multiple muscular variations from the neck to the lower extremities primarily on the left side were reported in a single cadaver [6]. They attributed this lack of symmetry to momentary disturbances in the formation of the embryonic somites.…”

“…During myogenesis, myoblasts form into migrating myofibers that are guided towards specific tendon attachment sites to establish connection with the skeletal system [5]. Errors may occur in migration that alter the attachment of muscle and tendon precursor cells, causing ectopic origins and insertions of muscular slips [6]. Therefore, the presence of the ASPS muscle may be a result of errors in the migration of muscle progenitors or tendinous attachment progenitors at the C1 level [7], due to alterations in the microenvironment through which the cells migrate, or Hox-gene related alterations in the axial identity of the progenitors [8].…”

Rare Fusion of the Semitendinosus and the Long Head of the Biceps Femoris Muscles in a Human Cadaver

“…Aberrant muscular bundles between the LBF and the semitendinosus muscle have been reported [11][12][13]. However, to the best of our knowledge, fusion of the muscle heads has not been reported in the reviewed literature.…”