CASE STUDY OF AN ANATOMICAL VARIATION OF THE BICEPS BRACHII MUSCLE

Date

2014-03

Authors

Jones, Michelle
Kalathil, Josin

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Abstract

During a dissection for anatomical understanding, we discovered an extra head to the biceps brachii muscle on one arm of our cadaver. Purpose (a): As part of a dissection aiming to increase anatomical understanding of the muscles and movements of the upper arm, a unilateral anatomical variation of the biceps brachii muscle was detected. A case study of the variant is presented. Methods (b): The dissection was performed on both embalmed arms of a 77 year old Caucasian female cadaver donated through the Willed Body Program at the University of North Texas Health Science Center. The epithelium and fascia were removed, and the pectoralis muscles, teres minor, and the deltoid were reflected in order to clearly view the underlying muscles along with their blood supplies and innervations. Results (c): Of the two arms observed, one was found to have an accessory muscle in the anterior arm. This muscle was located deep to the long head of the biceps brachii and distal to the attachment of the coracobrachialis. A branch of the musculocutaneous nerve provided innervation to this muscle, while blood was supplied by a branch from the brachial artery. Upon inspection, the origin appeared to be medial on the mid-shaft of the humerus. The muscle then merged and inserted into the radial tuberosity by a common tendon with the biceps brachii. Conclusions (d): This anatomic variant, known as supernumerary head of the biceps brachii, has been well documented in medical literature. Studies of the biceps brachii note that variation usually occurs with the origin of the supernumerary head and that it maintains a common insertion. The origin of the anomaly discovered and the fact that it is unilateral makes it one of the more commonly seen variations of the biceps brachii muscle.

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