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The clavicle, collarbone, or keybone is a slender, S-shaped long bone approximately 6 inches (15 cm) long [1] that serves as a strut between the shoulder blade and the sternum (breastbone). There are two clavicles, one on each side of the body.
Its lateral border is thick and irregular, and presents three or four tubercles for the tendinous origins of the deltoid.Its medial border, shorter than the lateral, is concave, gives attachment to a portion of the trapezius, and presents about its center a small oval surface for articulation with the acromial end of the clavicle.
The joint is formed by the sternal end of the clavicle, the clavicular notch of the sternum, and (the superior surface of) the costal cartilage of the first rib. [1] The articular surface of the clavicle is larger than that of the sternum, and is invested with a layer of cartilage, which is considerably thicker than that of the sternum. [1]
In digitless choanates, the cleithrum, clavicle, and interclavicle are dermal and linked to the caudal part of the head while the humerus articulates with a small scapulocoracoid bone. As the first digits appeared, the pectoral structure lost its direct connection to the head skeleton while the scapulocoracoid grew more prominent and started to ...
The acromioclavicular ligament, which attaches the clavicle to the acromion of the scapula. Superior acromioclavicular ligament. This ligament is a quadrilateral band, covering the superior part of the articulation, and extending between the upper part of the lateral end of the clavicle and the adjoining part of the upper surface of the acromion.
The clavicle articulates with the manubrium to form the anterior border of the thoracic outlet. Above the superior thoracic outlet is the root of the neck, and the superior mediastinum is inferiorly related.
This joint is unique among tetrapods, as in no other taxa is there a direct connection between the pectoral girdle and vertebral column (though in species with clavicles, the clavicle articulates with the sternum, which in turn is connected to the vertebrae via the ribs, allowing an indirect connection).
The articular disc of the sternoclavicular joint 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 ...