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SYNDESMOLOGY 



I 



part of the sternal end of the clavicle, and, passing obliquely downward and 

 inedialward, is fixed below to the back of the upper part of the manubrium sterni. 

 It is in relation, in front, with the articular disk and synovial membranes; behind, 

 with the Sternohyoideus and Sternothyreoideus. 



The Interclavicular Ligament (ligamentum interclamculare) . This ligament is a 

 flattened band, which varies considerably in form and size in different individuals, 

 it passes in a curved direction from the upper part of the sternal end of one clavicle 

 to that of the other, and is also attached to the upper margin of the sternum. It 

 is in relation, in front, wdth. the integument and Sternocleidomastoidei ; behind, 

 with the Sternothyreoidei. 



The Costoclavicular Ligament (ligamentum costoclaviculare; rhomboid ligament). 

 This ligament is short, flat, strong, and rhomboid in form. Attached below to 

 the upper and medial part of the cartilage of the first rib, it ascends obliquely 

 backward and lateralward, and is fixed above to the costal tuberosity on the under 

 surface of .the clavicle. It is in relation, in front, with the tendon of origin of the 

 Subclavius; behind, with the subclavian vein. 



FIG. 325. Sternoclavicular articulation. An terior view. 



The Articular Disk (discus articularis) . The articular disk is flat and nearly 

 circular, interposed between the articulating surfaces of the sternum and clavicle. 

 It is attached, above, to the upper and posterior border of the articular surface of 

 the clavicle; below, to the cartilage of the first rib, near its junction with the sternum ; 

 and by its circumference to the interclavicular and anterior and posterior sterno- 

 clavicular ligaments. It is thicker at the circumference, especially its upper and 

 back part, than at its center. It divides the joint into two cavities, each of which 

 is furnished with a synovial membrane. 



Synovial Membranes. Of the two synovial membranes found in this articulation, the lateral 

 is reflected from the sternal end of the clavicle, over the adjacent surface of the articular disk, 

 and around the margin of the facet on the cartilage of the first rib ; the medial is attached to the 

 margin of the articular surface of the sternum and clothes the adjacent surface of the articular 

 disk; the latter is the larger of the two. 



Movements. This articulation admits of a limited amount of motion in nearly every direc- 

 tion upward, downward, backward, forward, as well as circumduction. When these move- 

 ments take place in the joint, the clavicle in its motion carries the scapula with it, this bone 

 gliding on the outer surface of the chest. This joint therefore forms the center from which all 

 movements of the supporting arch of the shoulder originate, and is the only point of articulation 

 of the shoulder girdle with the trunk. The movements attendant on elevation and depression of 

 the shoulder take place between the clavicle and the articular disk, the bone rotating upon the 

 ligament on an axis drawn from before backward through its own articular facet; when the shoulder 

 is moved forward and backward, the clavicle, with the articular disk rolls to and fro on the 



