STERNO-CLAVICULAR. 207 



The Obturator Ligament is a dense membranous layer, consisting of fibres which, 

 interlace in various directions. It is attached to the circumference of the obtu- 

 rator foramen, which it closes completely, except at its upper and outer part, 

 where a small oval canal is left for the passage of the obturator vessels and nerve. 

 It is in relation, in front, with the Obturator externus ; behind, with the Obtura- 

 tor internus ; both of which muscles are in part attached to it. 



ARTICULATIONS OF THE UPPER EXTREMITY. 



The articulations of the Upper Extremity may be arranged into the following 

 groups: 1. Sterno-clavicular articulation. 2. Scapulo-clavicular articulation. 

 3. Ligaments of the Scapula. 4. Shoulder-joint. 5. Elbow-joint. 6. Radio- 

 ulnar articulation. 7. Wrist-joint. 8. Articulations of the Carpal bones. 9. 

 Carpo-metacarpal articulations. 10. Metacarpo-phalangeal articulations. IL 

 Articulations of the Phalanges. 



Fig. 130. Sterno-clavicular Articulation. Anterior View. 



1. STERNO-CLAVICULAR ARTICULATION. 



The Sterno-clavicular is an arthrodial joint. The parts entering into its forma- 

 tion are the sternal end of the clavicle, the upper and lateral part of the first 

 piece of the sternum, and the cartilage of the first rib. The articular surface of 

 the clavicle is much longer than that of the sternum, and invested with a layer 

 of cartilage, 1 which is considerably thicker than that on the latter bone. The 

 ligaments of this joint are the 



Anterior Sterno-clavicular. Interclavicular. 



Posterior Sterno-clavicular. Costo-clavicular or rhomboid. 



Interarticular Fibro-Cartilage. 



The Anterior Sterno-clavicular Ligament is a broad band of ligamentous fibres, 

 which covers the anterior surface of the articulation, being attached, above, to the 

 upper and front part of the inner extremity of the clavicle ; and, passing obliquely 

 downwards and inwards, is attached, below, to the front and upper part of the 

 first piece of the sternum. This ligament is covered in front by the sternal por- 



1 According to Bruch, the sternal end of the clavicle is covered by a tissue which is more 

 fibrous than cartilaginous in structure. 



