HUMERAL ARTICULATION OR SHOULDER-JOINT 317 



It is attached, by its apex, to the summit of the acromion just in front of the 

 articular surface for the clavicle; and by its broad base to the whole length of the 

 lateral border of the coracoid process. This ligament, together with the coracoid 

 process and the acromion, forms a vault for the protection of the head of the 

 humerus. It is in relation, above, with the clavicle and under surface of the Del- 

 toideus; below, with the tendon of the Supraspinatus, a bursa being interposed. 

 Its lateral border is continuous with a dense lamina that passes beneath the Del- 

 toideus upon the tendons of the Supraspinatus and Infraspinatus. The ligament 

 is sometimes described as consisting of two marginal bands and a thinner inter- 

 vening portion, the two bands being attached respectively to the apex and the 

 base of the coracoid process, and joining together at the acromion. When the 

 Pectoralis minor is inserted, as occasionally is the case, into the capsule of the 

 shoulder-joint instead of into the coracoid process, it passes between these two 

 bands, and the intervening portion of the ligament is then deficient. 



The Superior Transverse Ligament (ligamentum transversum scapulae superius; 

 transverse or suprascapular ligament). This ligament converts the scapular notch 

 into a foramen. It is a thin and flat fasciculus, narrower at the middle than at the 

 extremities, attached by one end to the base of the coracoid process, and by the 

 other to the medial end of the scapular notch. The suprascapular nerve runs 

 through the foramen; the transverse scapular vessels cross over the ligament. 

 The ligament is sometimes ossified. 



The Inferior Transverse Ligament (ligamentum transversum scapula' inferius; 

 spinoglenoid ligament) .This ligament is a weak membranous band, situated 

 behind the neck of the scapula and stretching from the lateral border of the spine 

 to the margin of the glenoid cavity. It forms an arch under which the transverse 

 scapular vessels and suprascapular nerve enter the infraspinatous fossa. 



III. Humeral Articulation or Shoulder-joint (Articulatio Humeri) (Fig. 326). 



The shoulder-joint is an enarthrodial or ball-and-socket joint. The bones 

 entering into its formation are the hemispherical head of the humerus and the 

 shallow glenoid cavity of the scapula, an arrangement \vhich permits of very 

 considerable movement, while the joint itself is protected against displacement 

 by the tendons which surround it. The ligaments do not maintain the joint sur- 

 faces in apposition, because when they alone remain the humerus can be separated 

 to a considerable extent from the glenoid cavity; their use, therefore, is to limit 

 the amount of movement. The joint is protected above by an arch, formed by 

 the coracoid process, the acromion, and the coracoacromial ligament. The artic- 

 ular cartilage on the head of the humerus is thicker at the center than at the cir- 

 cumference, the reverse being the case with the articular cartilage of the glenoid 

 cavity. The ligaments of the shoulder are: 



The Articular Capsule. The Glenohumeral. 



The Coracohumeral. The Transverse Humeral. 



The Glenoidal Labrum. 1 



The Articular Capsule (capsula articularis; capsular ligament} (Fig. 327). The 

 articular capsule completely encircles the joint, being attached, above, to the 

 circumference of the glenoid cavity beyond the glenoidal labrum; below, to the 

 anatomical neck of the humerus, approaching nearer to the articular cartilage 

 above than in the rest of its extent. It is thicker above and below than elsewhere, 

 and is so remarkably loose and lax, that it has no action in keeping the bones in 

 contact, but allows them to be separated from each other more than 2.5 cm., an 



1 The long tendon of origin of the biceps brachii also acts as one of the ligaments of this joint. See the observations 

 on page 287, on the function of the muscles passing over more than one joint. 





