38 ANATOMY IN A NUTSHELL. 



Ossification.— Its ossification is from two centers, one for the diaphysis, 

 the sixth week, or may be as early as the thirtieth day. which is the first in the 

 body, and the other a1 the sternal extremity, about the eighteenth or twen- 

 tieth year, complete ossification taking place about the twenty-fifth year. It 

 begins as a membranous bone, but the ossification later extends into the under 

 lying cartilage. 



Articulation. (Plate XII.) It articulates with the sternum, the cartilage 

 of the first rib and the acromion process of the scapula. The sterno-olavicu- 

 lar articulation is a reciprocal reception (saddle shaped-joint,) which belongs to 

 the diarthrodial class and has all the movements except rotation. The blood 

 supply of this joint i: — (1) the internal mammary from the subclavian. (2) 

 suprascapular from the thyroid axis. (3) superior thoracic from the first portion 

 of the axillary, and occasionally twigs from a muscular branch from the sub- 

 clavian which crosses the intersternal notch. The nerve supply to this joint 

 i~ , l the subclavian from the Brachial plexus and (2) the suprasternal from 

 the Cervical plexus. The ligaments are the anterior sterno-clavicular ligament 

 which is attached to the upper and anterior part of the manubrium; from here 

 it passes to be attached to the upper and anterior part of the sternal extremity 

 of the clavicle. The posterior sterno-clavicular ligament ha- a similar attach- 

 ment from the posterior surfaces of the same hones. These two make the cap- 

 sular ligament. The interarticular fibro-cartilage is thinner in the center than 

 at the circumference and gives attachment to the sternal end of the clavicle 

 above and the firsl costal cartilage at its junction with the manubrium below; 

 thus it divides the synovial membrane, having one on each side. 



The costo-clavicular or rhomboid ligament passes upward, backward and 

 outward from the sternal end of the cartilage of the first rib to the rhomboid 

 impression of the clavicle. The inter-clavicular ligament is a flat cross-band 

 attached to the upper margin of the manubrium, connecting the upper parts 

 of the inner end- of the clavicle. 



The acromlo-clavicular articulation is anarthrodial joint. (Plate XIII.) 

 The blood supply is (1) the suprascapular from the thyroid axis. (2)theacromio- 

 thoracic and (3) posterior circumflex. The nerve supply is (1) circum- 

 flex from the posterior cord of the Brachial plexus, (2) suprascapular, from 

 Brachial plexus and (3) supra-acromial from the Cervical plexns. The lig- 

 aments are the superior acromio-clavicular ligament, a quadrilateral band 

 which passes between ihe otiier end of the upper surface of the clavicle and the 

 upper surface of the acromion process. The inferior acromio-clavicular liga- 

 ment covers the joint below, but is thinner than the superior one. These two 

 make the capsular ligament. The interarticular fibro-cartilage is not always 

 present; it may fill the articulation, then there are two synovial 

 membrane-; more often it only occupies the upper part of the joint, then there 

 i> only one synovial membrane. The trapezoid ligament is the anterior and 

 externa] part of the coraco-clavicular ligament and is attached above to the 

 oblique line of the under surface of ihe clavicle and below to the posterior half 

 of the upper surface of the coracoid process. The conoid ligament is the pos- 

 terior and internal pari of ihe coraco-clavicular ligament and is attached above 



