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In human anatomy, the biceps brachii (), commonly known as the biceps, is a two-headed muscle that lies on the upper arm between the shoulder and the elbow. Both heads arise on the scapula and join to form a single muscle belly which is attached to the upper forearm. While the biceps crosses both the shoulder and elbow joints, its main function is at the latter where it flexes the forearm at the elbow and supinates the forearm. Both these movements are used when opening a bottle with a corkscrew: first biceps unscrews the cork (supination), then it pulls the cork out (flexion). ==Structure== When the humerus is in motion, the tendon of the long head is held firmly in place in the intertubercular groove by the greater and lesser tubercles and the overlying transverse humeral ligament. During the motion from external to internal rotation, the tendon is forced medially against the lesser tubercle and superiorly against the transverse ligament. The tendon of the short head runs adjacent to the tendon of the coracobrachialis and likewise attaches to the coracoid process. Both heads join on the middle of the humerus, usually near the insertion of the deltoid, to form a common muscle belly. Distally, biceps ends in two tendons: the stronger attaches to (inserts into) the radial tuberosity on the radius, while the other, the bicipital aponeurosis, radiates into the ulnar part of the antebrachial fascia. The tendon that attaches to the radial tuberosity is partially or completely surrounded by a bursa; the bicipitoradial bursa, which ensures frictionless motion between the biceps tendon and the proximal radius during pronation and supination of the forearm. Two additional muscles lie underneath the biceps brachii. These are the coracobrachialis muscle, which like the biceps attaches to the coracoid process of the scapula, and the brachialis muscle which connects to the ulna and along the mid-shaft of the humerus. Besides those, the brachioradialis muscle is adjacent to the biceps and also inserts on the radius bone, though more distally. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Biceps」の詳細全文を読む スポンサード リンク
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