254 



THE ARTICULATIONS 



of joints, the large upper end of the humerus playing upon the shallow glenoid 

 cavity. Like the hip, it is a ball-and-socket joint. It is retained in position 

 much less by ligaments than by muscles, and, o^ving to the looseness of its cap- 

 sule, as well as to all the other conditions of its construction and position, it is 

 exceedingly liable to be displaced; on the other hand, it is sheltered from violence 

 by the two projecting processes — the acromion and coracoid. 

 The ligaments of the shoulder-joint are: — 



Articular capsule. 

 Gleno-humeral. 



Coraco-humeral. 

 Glenoid. 



The articular capsule (figs. 286, 287, and 288) is a loose sac, insufficient in 

 itself to maintain the bones in contact. It consists of fairly distinct but not 

 coarse fibres, closely woven together, and directed, some straight, others ob- 

 liquely, between the two bones, a few circular ones being interwoven amongst 

 them. At the scapula, it is fixed on the dorsal aspect to the prominent rough 



Fig. 288. — Vertical Section through the Shoulder-joint to show the Gleno-humeral 



Ligament. 

 (The joint is opened from behind.) 



Supraspinatus muscle 



Subacromial bursa 

 Tendon of biceps with 

 gleno-humeral liga- 

 ment 



Tendon of subscap-^ 

 ulari:: 



Articular capsule -j- 



Superior trans- 

 verse ligament 



surface around the margin of the glenoid cavity, reaching as far as the neck of 

 the bone. Superiorly, it is attached to the root of the coracoid process; an- 

 teriorly, to the ventral surface, at a variable distance from the articular margin, 

 often reaching half an inch (12 mm.) upon the neck of the bone, and thus allow- 

 ing the formation of a pouch; it may not, however, extend for more than a 

 quarter of an inch (6 mm.) beyond the articular margin; inferiorly, it blends with 

 the origin of the long head of the triceps. At the humerus, the superior half is 

 fixed to the anatomical neck, sending a prolongation downward between the two 

 tuberosities which attenuates as it descends, and covers the transverse humeral 

 ligamf-nt. The lower half of the capsule descends upon the humerus further 

 from the articular margin, some of the deeper fibres being reflected upward so 

 as to be attached close to the articular edge, thus forming a kind of fibrous in- 

 vestment for the neck of the humerus. This ligament is more uniform in thickness 

 than that of the hip. 



Gleno-humeral bands of the capsule (figs. 288 and 289). — There are three 

 accessory bands, known as the superior, middle and inferior gleno-humeral hands, 

 which project toward the interior of the joint from the fore part of the capsule 

 and are consequently best seen when the joint is opened from behmd. 



The middle band reaches from the anterior margin of the glenoid cavity along the lower 

 border of the subscapularis tendon to the lower border of the lesser tuberosity, and the inferior 

 band from the inferior part of the glenoid cavity to the inferior part of the neck of the humerus. 



