326 



A MANUAL OF ANATOMY 



arises in part from it. The interclavicular ligament is a well- 

 marked, curved bundle of fibres, which is attached at either side 

 to the upper and back part of the inner end of the clavicle. In 

 crossing between the two bones it curves downwards to be attached 

 to the interclavicular notch on the upper border of the presternum. 

 The costo-clavicular or rhomboid ligament is a strong, quadrilateral 

 band of fibres, which extends from the upper surface of the first 

 costal cartilage to the rhomboid impression on the under surface 

 of the clavicle, its direction being upwards, backwards, and 

 outwards. 



The interarticular fibro-cartilage is a nearly circular, flattened 

 plate, which is thinner at the centre and lower part than elsewhere. 

 It is attached superiorly to the upper and back part of the inner end 

 of the clavicle, and interiorly to the inner end of the first costal car- 

 tilage, where it inclines slightly outwards to form part of a socket 



Interclavicular 

 Ligament 

 Anterior Sterno-clavicular Ligament j Interarticular Fibro-cnitilage 



CLAVICLE ^^ 

 Costo-clavicular __WKJjji.o. s^^^lis^'Ss 



or Rhomboifl >\v5^^»^-v:^sr%^'^ 



Ligament 'fffi-'}!^^~^^ 



Fig. 182. — The Sterno-Clavicular Joints. . 

 (The Left Anterior Sterno-clavicular Ligament has been remove^.) 



for the lower portion of the inner end of the clavicle. Its circura-- 

 ference is connected with the fibrous capsule of the joint. The plate 

 sometimes presents a perforation at its centre. 



There are two synovial membranes at this joint, one on eitherj 

 side of the interarticular fibro-cartilage. When the latter is per- 

 forated these are continuous with each other. 



Arterial Supply. — The suprasternal branch of the suprascapular,] 

 and the internal mammary. 



Nerve-supply. — The suprasternal branch of the cervical plexus. 



Movements. — These take place in an upward, downward, forward, and bacW 

 ward direction. There is also circumduction. In the upward and downwaro 

 movements the clavicle moves on the fibro-cartilage, and the forward and 

 backward movements take place between the fibro-cartilage and the pre-^ 

 sternum. In the downward movement of the bone the interarticular ligamenl 

 is put upon the stretch, and the upward movement is limited by the costoJ 

 clavicular ligament. 



Acromio-clavicular Joint. — This belongs to the class diarthrosis, 

 and to the subdivision arthrodia. The articular surfaces arc the 

 outer end of the clavicle and the facet on the acromion process. 



