Histological and immunohistochemical evaluation of mechanoreceptors and nociceptors in the long head of biceps brachii muscle

Biceps brachii muscle is a 2-headed muscle on the front of the arm. The long head arises from the supraglenoid tuberculum at the superior margin of the glenoid cavity, and glenoidal labrum. The short head called caput breve arises from coracoid process. The common tendon ends at the rough back of the radial tuberosity. Some aponeurotic fibers expanding medially to the tendon are called aponeurosis musculi bicipitis brachii (aponeurosis bicipitalis; lacertus fibrosus), which interfere with the deep fascia that surrounds the forearm flexor muscles. Biceps brachii is a powerful supinator. It flexes the elbow – most effectively, with the forearm supinated – and acts, to a slight extent, as a flexor of the shoulder joint.. It is innervated by musculocutaneous nerve. Tendon of caput longum has been regarded as a pain generator. The contribution of the shoulder joint to the proprioceptive sensation is a debate topic. In our study; we used 15 right 15 left fresh frozen cadaver arm. We aimed to describe the mechanoreceptors and nociceptors of the biceps brachii caput longum tendon by excising the tendon. We separated the tendon into four parts; extracapsulary, sulcus intertubercularis, intracapsulary and origo part. With immunohistochemical staining in extracapsulary part Pacini corpuscle, Ruffini corpuscle, Golgi tendon organ and free nerve endings were detected and all specimens showed immunoreactivity for Ruffini corpuscle and free nerve endings. At the end of our efforts the finding of mechanoreceptors and nociceptors in the tendon of Caput longum leads to the conclusion that the long head of biceps brachii has a potential proprioceptive role for the shoulder joint. Key words: mechanoreceptor, nociceptor, immunohistochemistry, tendon, biceps brachii