I040 A MANUAL OF ANATOMY 



of the spinal canal, and as they extend between the neural arches 

 they close in the canal in these situations. Each ligamentura 

 subflavum extends from the root of the articular process to the 

 place where the lamina joins its fellow to form the spinous process. 

 At this point it comes into relation with the ligament of the opposite 

 side, a small interval being left between the two for the passage of 

 veins. Superiorly the ligament is attached to the anterior surface 

 of the upper lamina a little above its lower border, and inferiorly 

 it is attached to the upper border, and adjacent part of the posterior 

 surface, of the lower lamina. The ligamenta subflava are wider 

 in the cervical and lumbar regions than in the thoracic region, and 

 over the greater part of the latter region, as viewed from the 

 exterior, they are concealed from view by the imbricated laminae. 

 Their importance consists in their great elasticity, which enables 

 them to maintain the vertebral column erect, and to restore it to 

 the erect position after it has been bent forwards. 



3. Ligaments of the Articular Processes. — ^The joints between the 

 articular processes belong to the class diarthrosis, and to the sub- 

 division arthrodia. The articular surfaces are covered by cartilage, 

 and the joint is surrounded by a capsular ligament, lined with a 

 synovial membrane. These ligaments are disposed more loosely 

 in the cervical region than elsewhere. 



4. Ligaments of the Spinous Processes. — ^These are supraspinous 

 and interspinous. 



The supraspinous ligament consists of longitudinal fibres which 

 connect the extremities of the spinous processes. It extends from 

 the spine of the seventh cervical vertebra to the spine of the fourth 

 sacral segment, and its fibres are arranged in a manner similar to 

 those of the anterior common ligament. In the cervical region 

 the supraspinous ligament is replaced by the ligamentum nuchae. 

 The interspinous ligaments, which are thin and membranous, are 

 situated between adjacent spinous processes, to the margins of 

 which they are attached from root to tip. They are strongest in 

 the lumbar region, and in the neck they are replaced by deep pro- 

 cesses of the ligamentum nuchas. 



5. Ligaments of the Transverse Processes. — ^These consist of 

 scattered fibres, which pass between the extremities of the trans- 

 verse processes in the thoracic and lumbar regions. In the neck 

 they are replaced by the intertransversales muscles. 



Movements. — The movements allowed in the vertebral column are flexion, 

 extension, lateral movement, rotation, and circumduction. 



Flexion and extension are freely allowed in the cervical and lumbar regions. 

 In the thoracic region these movements are very limited on account of (i) the 

 small amount of intervertebral substance, and (2) the imbrication of the 

 lamina?. Lateral flexion is allowed in the cervical, thoiacic, and lumbar 

 regions, but in the neck it is associated with rotation. During these com- 

 bined movements of lateral flexion and rotation in the neck one inferior 

 articular process glides upwards and forwards on that which is opposed to 

 it, whilst the other inferior articular process glides downwards and backwards 

 on the one opposed to it. Pure rotation is allowed in the thoracic region 

 round an axis corresponding with the centre of a circle of which the surfaces 



