ARTICULAR SURFACE 3 

 FOR TUBERCLE 

 OF RIB 



ANTERIOR 

 COSTOTRANS- 

 VERSE LIGAMENT 

 INTERTRANS- 

 VERSE LIGAMENT 



SUPERIOR ARTICULAR 

 SURFACE FOR HEAD 

 DF RIB 



INTCRVEHTE- 

 'BRAL DISK 



ARTICULATIONS OF THE RIBS WITH THE VERTEBRAE 285 



section should be made across the transverse process and corresponding part 

 of the rib; or the rib may be forcibly separated from the transverse process and 

 the fibres of the ligament put on the stretch. 



For the eleventh and twelfth ribs this ligament is quite rudimentary or wanting. 



The posterior COStotransverse ligament (ligamentum costotransversarium pos- 

 terius) (Fig. 234) is a short but thick and strong fasciculus which passes obliquely 

 from the summit of the transverse process to the rough nonarticular portion of 

 the tubercle of the rib. 

 This ligament is shorter 

 and more oblique in the 

 upper than in the lower 

 ribs. Those correspon- 

 ding to the superior ribs 

 ascend, while those of 

 the inferior ribs descend 

 slightly. 



For the eleventh and 

 twelfth ribs this ligament 

 is wanting. 



The capsular liga- 

 ment (capsula articular- 

 is} is a thin, membranous 

 sac attached to the cir- 

 cumference of the articu- 

 lar surfaces, and enclos- 

 inga synovial membrane. 



For the eleventh and 

 twelfth ribs this ligament 

 is absent. 



Movements. The heads 

 of the ribs are so closely 

 connected to the bodies of 

 the vertebrae by the stellate 

 and intra-articular ligaments, 

 and the necks and tubercles 

 of the ribs to the transverse 

 processes, that only a slight 

 gliding movement of the ar- 

 ticular surfaces on each other can take place in these articulations. The result of this gliding 

 movement with respect to the six upper ribs consists in an elevation of the front and middle 

 portion of the rib with a consequent enlargement of the antero-posterior diameter of the thorax, 

 the hinder part being prevented from performing any upward movement by its close connection 

 with the vertebral column. In this gliding movement the rib rotates on an axis corresponding 

 to a line drawn through the two articulations, costocentral and costotrans verse, which the rib 

 forms with the vertebral column. None of the ribs lie in a truly horizontal plane; they are all 

 directed more or less obliquely, so that their anterior extremities lie at a lower level than their 

 posterior; this obliquity increases from the first to the seventh, and then again decreases. If we 

 examine any one rib say that in which there is the greatest obliquity we shall see that it is 

 obvious that as its sternal extremity is carried upward it must also be thrown forward; so that 

 the rib may be regarded as a radius moving on the vertebral joint as a centre, and causing the 

 sternal attachment to describe an arc of a circle in the vertical plane of the body. Since all the 

 ribs are oblique and connected in front to the sternum by the flexible costal cartilages, they 

 must have a tendency to thrust the sternum forward, and so increase the antero-posterior diameter 

 of the thorax. With respect to the seventh, eighth, ninth, and tenth ribs, each one, besides rotating 

 in a similar manner to the upper six, also rotates on an axis corresponding with a line drawn from 

 the head of the rib to the sternum. By this movement an elevation of the middle portion of the 

 rib takes place, and consequently an increase in the transverse diameter of the thorax. For the 

 ribs not only slant downward and forward from their vertebral attachment, but they are also 

 oblique in relation to their transverse plane that is to say, their middle is at a lower level than 



INFERIOR ARTICULAR 

 SURFACE FOR HEAD 

 OF RIB 

 R ARTIC- 

 ULAR PROCESS 



FIG. 235. Ribs and corresponding vertebrae with ligaments, viewed from 

 the right. (Spalteholz.) 



