134 ARTHROLOGY, OR ANATOMY OF ARTICULATIONS 



The transverse humeral ligament is a part of the capsule 

 between the tuberosities. 



When the joint is viewed from the inside, there are three 

 supplementary bands seen on the anterior part of the capsule. 

 The highest is the glenoideohumeral or Flood's ligament, which 

 passes from the upper part of the anterior margin of the glenoid 

 cavity to the upper end of the bucipital groove. The middle 

 band is the internal glenoideobrachiale of Schlemm. It is a 

 thin fold arising from the same point as the preceding ligament. 

 It descends obliquely outward to be lost on the capsule beneath 

 the subscapular tendon, passing to the small tuberosity (Quain). 

 The lowest band is the ligamentum glenoideobrachiale inferior, 

 or broad ligament of Schlemm, which rises from the middle 

 of the anterior margin of the glenoid cavity and passes down 

 and out parallel to the internal ligament of Schlemm to the 

 under portion of the neck of the humerus. 



The head of the humerus is held in place by the subscapularis, 

 supraspinatus, infraspinatus, deltoid, biceps, and triceps 

 muscles, and also by atmospheric pressure. 



The nerves supplying the joint are circumflex and supra- 

 scapular. 



The arteries are anterior and posterior circumflex and supra- 

 scapular. 



The movements of the joint are in every direction. 



Flexion is possible to 45 degrees without involving other 

 joints, produced by the pectoralis major, anterior fibers of 

 the deltoid, coracobrachialis, and by the biceps if the elbow 

 is fixed. This occurs on a transverse axis through the great 

 tuberosity and glenoid cavity. Flexion is limited by tension 

 of the posterior part of the capsule and by the small tuberosity 

 abutting against the coracoid; the movement is continued 

 by rotation of the scapula. 



Extension through 15 degrees is produced by the latissimus 

 dorsi, teres major, posterior fibers of the deltoid, and the triceps 

 if the elbow is fixed. Extension is hindered by superior muscles 

 and approximation of the great tuberosity and acromion. 



Abduction through 90 degrees is performed by the deltoid, 

 aided by the supraspinatus, on an anteroposterior axis through 

 the anatomical neck of the humerus; further motion calls into 

 play accessory joints, viz., the upper portion of the trapezius 

 elevates the peak of the shoulder, and the lower fibers of the 



