The scapulohumeral articulation (shoulder joint) is an enarthrodial (ball and socket) joint but because of its being held more or less firmly against the thoracic wall by muscular and tendinous attachment, and because a part of this attachment affords a means of support for the body itself, there is no need for binding ligaments and movement is possible in all directions even though restricted as to extent.
Fig. 2—Muscles of Left Thoracic Limb from Elbow Downward; Lateral (External) View.
a, Extensor carpi radialis; g, brachialis; g', anterior superficial pectoral; c, common digital extensor; e, ulnaris lateralis. (After Ellenberger-Baum, Anat. für Künstler.) (From Sisson's "Anatomy of the Domestic Animals").
Fig. 3—Muscles of Left Thoracic Limb from Elbow Downward; Medial (Internal) View.
The fascia and the ulnar head of the flexor carpi ulnaris have been removed. 1, Distal end of humerus; 2, median vessels and nerve. (From Sisson's "Anatomy of the Domestic Animals").