300 SYNDESMOLOGY 



costochondral angle is opened out. By these latter movements a considerable increase in the 

 transverse diameter of the thorax is effected. 



Verlebrochondral Ribs (Fig. 318). The seventh rib is included with this group, as it conforms 

 more closely to their type. While the movements of these ribs assist in enlarging the thorax 

 for respiratory purposes, they are also concerned in increasing the upper abdominal space for 

 viscera displaced by the action of the diaphragm. The costal cartilages articulate with one 

 another, so that each pushes up that above it, the final thrust being directed to pushing forward 

 and upward the lower end of the body of the sternum. The amount of elevation of the anterior 

 extremities is limited on account of the very slight rotation of the rib neck. Elevation of the 

 shaft is accompanied by an outward and backward movement; the outward movement everts 

 the anterior end of the rib and opens up the subcostal angle, while the backward movement 

 pulls back the anterior extremity and counteracts the forward thrust due to its elevation; this 

 latter is most noticeable in the lower ribs, which are the shortest. The total result is a consider- 

 able increase in the transverse and a diminution in the median antero-posterior diameter of the 

 upper part of the abdomen; at the same time, however, the lateral antero-posterior diameters of 

 the abdomen are increased. 



Vertebral Ribs. Since these ribs have free anterior extremities and only costocentral articula- 

 tions with no interarticular ligaments, they are capable of slight movements in all directions. 

 When the other ribs are elevated these are depressed and fixed to form points of action for the 

 diaphragm. 



VIII. Articulation of the Vertebral Column with the Pelvis. 



The ligaments connecting the fifth lumbar vertebra with the sacrum are similar 

 to those which join the movable segments of the vertebral column with each other 

 viz.: 1. The continuation downward of the anterior and posterior longitudinal 

 ligaments. 2. The intervertebral fibrocartilage, connecting the body of the fifth 

 lumbar to that of the first sacral vertebra and forming an amphiarthrodial joint. 

 3. Ligamenta flava, uniting the laminae of the fifth lumbar vertebra with those 

 of the first sacral. 4. Capsules connecting the articular processes and forming 

 a double arthrodia. 5. Inter- and supraspinal ligaments. 



On either side an additional ligament, the iliolumbar, connects the pelvis with 

 the vertebral column. 



The Iliolumbar Ligament (ligamentum iliolumbale) (Fig. 319). The iliolumbar 

 ligament is attached above to the lower and front part of the transverse process 

 of the fifth lumbar vertebra. It radiates as it passes lateralward and is attached 

 by two main bands to the pelvis. The lower bands run to the base of the sacrum, 

 blending with the anterior sacroiliac ligament; the upper is attached to the crest 

 of the ilium immediately in front of the sacroiliac articulation, and is continuous 

 above with the lumbodorsal fascia. In front, it is in relation with the Psoas major; 

 behind, with the muscles occupying the vertebral groove; above, with the Quadratus 

 lumborum. 



IX. Articulations of the Pelvis. 



The ligaments connecting the bones of the pelvis with each other may be divided 

 into four groups: 1. Those connecting the sacrum and ilium. 2. Those passing 

 between the sacrum and ischium. 3. Those uniting the sacrum and coccyx. 4. 

 Those between the two pubic bones. 



1. Sacroiliac Articulation (articulatio sacroiliaca). The sacroiliac articulation 

 is an amphiarthrodial joint, formed between the auricular surfaces of the sacrum 

 and the ilium. The articular surface of each bone is covered with a thin plate 

 of cartilage, thicker on the sacrum than on, the ilium. These cartilaginous plates 

 are in close contact with each other, and to a certain extent are united together 

 by irregular patches of softer fibrocartilage, and at their upper and posterior part 

 by fine interosseous fibers. In a considerable part of their extent, especially in 

 advanced life, they are separated by a space containing a synovia-like fluid, and 

 hence the joint presents the characteristics of a diarthrosis. The ligaments of the 

 joint are: 



The Anterior Sacroiliac. The Posterior Sacroiliac. 



The Interosseous. 



