Macroscopic organization and sensitive innervation of the tendinous intersection and the lacertus fibrosus of the biceps brachii muscle in the ass and horse.

The most developed and organized lamina running trough the biceps brachii muscle belly forms a well-marked tendinous intersection connecting the proximal tendon with the distal one. Moreover, the lacertus fibrosus arises from this lamina close to the distal tendon and blends with the fascia of the forearm and joins the extensor carpi radialis muscle. The nerve supply for the biceps tendinous intersection arises from the intramuscular rami of the musculo-cutaneous nerve, whereas the lacertus fibrosus is provided with some cutaneous rami of the same nerve. The biceps brachii tendinous intersection and lacertus fibrosus are provided with free and encapsulated nervous endings. The encapsulated corpuscles are represented by rare Pacini, Pacini-like and Ruffini receptors and by numerous Golgi tendon-organs. All these receptors have been studied by a topographical point of view and the role played by the proprioceptors in synchronizing shoulder, elbow and carpal joint movements both in the flexion and the extension of the limb, has been hypothesized.