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Henry Gray (1825–1861).  Anatomy of the Human Body.  1918.
 
part of the sternal end of the clavicle, and, passing obliquely downward and medialward, 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 interclaviculare).—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, with 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. Anterior view. (See enlarged image)


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 sternoclavicular 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 direction—upward, downward, backward, forward, as well as circumduction. When these movements 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

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