ABDOMINAL WALL 397 



Anteriorly the fibres of the transversus abdominis muscle 

 end in a strong aponeurosis, which is inserted into the linea 

 alba, the pubic crest, and the ilio-pectineal line. Towards 

 this aponeurosis the fleshy fibres for the most part run in 

 a transverse direction. The lower fibres, however, take a 

 curved course downwards and medially, so that the muscle 

 presents an arched lower margin. 



The dissector has already seen that the lowest portions of 

 the aponeuroses of the internal oblique and the transverse 

 muscles blend to form the falx inguinalis or conjoined tendon. 

 It is through the medium of this tendon that the transversus 

 abdominis gains its insertion into the pubic crest and into the 

 pecten pubis. The aponeurosis of the transversus abdominis 

 constitutes the greater portion of the falx inguinalis indeed, 

 whereas the internal oblique aponeurosis has an attachment 

 to the pecten pubis of little more than half an inch, the 

 aponeurosis of the transversalis is fixed to fully an inch of 

 this crest. 



Above the level of the falx inguinalis the aponeurosis 

 of the transversus is inserted into the linea alba, but in 

 passing medially to this insertion it presents two different 

 relations to the rectus muscle. Down to a point midway 

 between the umbilicus and pubes it passes behind the rectus, 

 and blends with the posterior lamella of the aponeurosis of 

 the internal oblique. Below this point it passes in front of 

 the rectus, and blends with the aponeuroses of the internal 

 oblique and external oblique. 



Dissection. The sheath of each rectus should now be opened by a 

 vertical incision along the middle line of the muscle. The divided anterior 

 lamella should then be carefully raised from the surface of the muscle 

 and turned laterally and medially. At the linese transversse this can 

 only be done with difficulty, so close is the connection between the sheath 

 and the tendinous intersections of the muscle. 



Contents of the Sheath of the Rectus. Within the rectal 

 sheath we find the following structures : 



1. The rectus muscle. 



2. The pyramidalis muscle. 



3. The terminal portions of the anterior branches of the seven lower 



thoracic nerves. 



4. The inferior epigastric artery. 



5. The superior epigastric artery. 



In cleaning the rectus keep in mind the thoracic nerves. 

 These will now be seen to enter the sheath and sink into the 



