ABDOMINAL WALL 



395 



M. Transversus Abdominis (O.T. Transversalis Muscle). 

 This is the deepest of the three muscular strata which enter 

 into the formation of the wall of the abdomen. It has a 

 threefold origin^ viz. from the pelvis, from the vertebral 

 column, and from the costal cartilages. By its pelvic origin 

 it is attached to the lateral third of the inguinal ligament and 

 to the anterior two-thirds of the medial lip of the crest of the 

 ilium ; by its costal origin it arises from the inner surfaces of 

 the costal cartilages of the lower six ribs, by a series of slips 

 or digitations which interdigitate with the slips of origin of 



Psoas 

 magnus 



Quadratus 

 lumborum 



Sacrospinalis 



Fascia 

 transversalis 



Paternal 

 oblique 



Internal 

 oblique 

 Transversus 

 abdominis 



Latissimus 

 dorsi 



Serratus 

 post. inf. 



FIG. 148. Lumbar fascia and sheath of Rectus abdominis. 

 The dotted line represents the Peritoneum. 



the diaphragm ; by its vertebral origin it is attached, through 

 the medium of the lumbar fascia, to the spinous processes, and 

 the tips and roots of the transverse processes, of the lumbar 

 vertebrae. In point of fact, the lumbar fascia constitutes the 

 posterior aponeurosis of this muscle. But the manner in 

 which this fascia is attached to the vertebrae requires further 

 explanation. As it approaches the spine it splits into three 

 layers or lamellae ; of these the posterior lamella is attached 

 to the tips of the spinous processes, the anterior lamella to 

 the roots of the transverse processes, and the intermediate 

 lamella to the tips and adjacent sides of the transverse 

 processes. Two aponeurotic compartments are thus formed, 



