INTRA-ARTICULAR LIGA- 

 MENT OF HEAD OF RIB 



ARTICULATIONS OF THE RIBS WITH THE VERTEBRA 283 



surface. The superior fibres pass upward to be connected with the body of 

 the vertebra above; the inferior one descends to the body of the vertebra below; 

 and the middle one, the smallest and least distinct, passes horizontally inward, 

 to be attached to the intervertebral substance. 



On the first rib, w r hich articulates with a single vertebra, this ligament does 

 not present a distinct division into three fasciculi; its fibres, however, radiate, 

 and are attached to the body of the last cervical vertebra, as well as to the body 

 of the vertebra with which the rib articulates. In the tenth, eleventh, and twelfth 

 ribs also, which likewise articulate with a single vertebra, the division does not 

 exist; but the fibres of the ligament in each case radiate and are connected with 

 the vertebra above, as well as that with which the ribs articulate. 



Relations. In front, with the thoracic ganglia of the sympathetic, the pleura, and, on the 

 right side, with the vena azygos major; behind, with the interarticular ligament and synovial 

 membranes. 



The capsular ligament (capsula articularis) is a thin and loose ligamentous 

 bag, which surrounds the joint between the head of the rib and the articular 

 cavity formed by the inter- 

 vertebral disk and the ad- 

 jacent vertebra. It is very 

 thin, firmly connected with 

 the anterior ligament, and 

 most distinct at the upper 

 and lower parts of the 

 articulation. Behind, some 

 of its fibres pass through 

 the intervertebral foramen 

 to the back of the inter- 

 vertebral disk. This is the 

 homologueof theligamenttim 

 cotijugale of some mammals, 

 which unites the heads of 

 opposite ribs across the 

 back of the intervertebral 

 disk. 



The intra-articular liga- 

 ment (lig amentum capituli 

 costae inter articular e) (Figs. 

 233 and 234) is situated in 

 the interior of the joint. It 

 consists of a short band of 



fibres, flattened from above downward, attached by one extremity to the sharp 

 crest which separates the two articular facets on the head of the rib, and by the 

 other to the intervertebral disk. It divides the joint into two cavities, which 

 have no communication with each other. For the first, tenth, eleventh, and 

 twelfth ribs the intra-articular ligament does not exist; consequently there is 

 but one synovial membrane. 



FIG. 233. Ribs and corresponding vertebral bodies with their 

 ligaments, viewed from the right. (Spalteholz.) 



Synovial Membranes (Figs. 233 and 234). There are two synovial membranes in each of 

 the articulations in which there is an intra-articular ligament, one on each side of this structure. 



