LIGAMENTS OF THE RIBS. 145 



lu the first , eleventh, and twelfth ribs, the three fasciculi are attached 

 lo the body of the corresponding vertebra. 



The capsular ligament is a thin layer of ligamentous fibres, surrounding 

 the joint in the interval left by the anterior ligament ; it is thickest above 

 and below the articulation, and protects the synovial membranes. 



The inter articular ligament is a thin band which passes between the 

 sharp crest on the head of the rib and the intervertebral substance. It 

 divides the joint into two cavities, which are each furnished with a sepa- 

 rate synovial membrane. The first, eleventh, and twelfth ribs have no 

 interarticular ligament, and consequently but one synovial membrane. 



The anterior costo-transverse ligament is a broad band composed of 

 several fasciculi, which ascends from the crest-like ridge on the neck 

 of the rib, to the transverse process immediately above. This liga- 

 ment separates the anterior from the posterior branch of the intercostal 

 nerves. 



The middle costo-transverse ligament is a very strong interosseous liga- 

 ment, passing directly between the posterior surface of the neck of the rib, 

 and the transverse process against which it rests. 



The posterior costo-transverse ligament is a small but strong fasciculus, 

 passing obliquely from the tubercle of the rib, to the apex of the trans- 

 verse process. The articulation between the tubercle of the rib and the 

 transverse process is provided with a small synovial membrane. 



There is no anterior costo-transverse ligament to the first rib ; and only 

 rudimentary posterior costo-transverse ligaments to the eleventh and 

 twelfth ribs. 



Actions. The movements permitted by the articulations of the ribs, 

 are upwards and downwards, and slightly for- 

 wards and backwards ; the movement increas- Fig. 82.* 

 ing in extent from the head to the extremity of 

 the rib. The forward and backward move- 

 ment is very trifling in the seven superior, but 

 greater in the inferior ribs ; the eleventh and 

 twelfth are very movable. 



7. Articulation of the Ribs with the Sternum, 

 and with each other. The ligaments of the 

 costo-sternal articulations are, 



Anterior costo-sternal, 

 Posterior costo-sternal, 

 Superior costo-sternal, 

 Inferior costo-sternal, 

 Synovial membranes. 



The anterior costo-sternal ligament is a thin band of ligamentous fibres 

 that passes in a radiated direction from the extremity of the costal carti- 

 lage to the anterior surface of the sternum, and intermingles its fibres with 

 those of the ligament of the opposite side and with the tendinous fibres of 

 origin of the pectoralis major muscle. 



* A posterior view of a part of the thoracic portion of the vertebral column, showing 

 the ligaments connecting the vertebrae with each other, and the ribs with the vertebrae. 

 J, 1. The supra-spinous ligament. 2, 2. The ligamenta subflava, connecting tho 

 laminae -3. The anterior costo-transverse ligament. 4. The posterior costo-transvffrsa 

 ligaments. 



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