34. Anatomy of Skeleton 



These origins from the fronts of the transverse processes account for the presence of the lumbar 

 nerves in the substance of the Psoas, for it is apparent that each nerve as it turns down over the 

 front of the transverse process next below (see Fig. 35), must lie on a part of the muscle and so 

 enter its substance ; the ilio-inguinal and ilio-hypogastric nerves do not cross a transverse process, 

 so they lie behind the muscle and emerge from under its outer border, and the fifth lumbar nerve 

 also does not lie in the muscle, whereas the lower part of the fourth, passing down to join it across 

 the fifth transverse process, must run in the muscle for a short part of its course. 



There are tendinous and muscular fibres between the transverse processes, and 

 markings for these may be found on the upper and lower edges of the processes and 

 adjacent parts of the posterior surface. 



The middle or main lamella of the aponeurosis of origin of the Transversalis is 



lumba.r 



dorsal. 



cervical 



FIG. 28. Schemes to show the effect of the shape of the articular processes on the move- 

 ment of rotation between the bodies. A is approximately the centre round which 

 rotation takes place ; B is part of the circumference of a circle drawn round A and 

 passing through the articular processes. It is clear that the shape and plane of these 

 processes in the lumbar and cervical regions inhibits any rotation between the vertebral 

 bodies. 



attached to the outer end of the transverse process, extending on to its back surface, 

 where a roughened area near the tip marks its connection with the bone. Fibres 

 radiate out from each process into this aponeurotic sheet, as shown in Fig. 35, and 

 these are modified above into the costo-lumbar ligamentous attachments and below 

 into the ilio-lumbar ligament ; between these they open out into the middle lamella. 

 The lamella is thin between the processes, and has some inter-transverse fibres in it 

 which are probably part of the inter-transverse musculo-tendinous system, with the 

 fasciae of which it otherwise blends. 



The Quadratus lumborum lies in front of this middle lamella and also covers the 

 outer end of the transverse processes, to the upper and lower parts of which it is 

 attached : the muscle is covered by the anterior lamella, and this reaches the trans- 

 verse processes at the inner margin of the Ouadratus, under cover of Psoas. Thus a 



