394 ABDOMEN 



Nerves of the Abdominal Wall. Running forwards upon 

 the transversus abdominis muscle, the dissector will find the 

 following nerves : 



1. The anterior branches of the lower seven thoracic nerves. 



2. The ilio-hypogastric nerve. \From the anterior branch of the first 



3. The ilio-inguinal nerve. / lumbar nerve. 



The seven lower thoracic nerves enter the abdominal wall at 

 the margin of the costal arch, where they insinuate themselves 

 between the internal oblique and the transversus abdominis 

 muscle. Then they run to the lateral border of the rectus 

 muscle, where they disappear by piercing and passing within 

 the sheath of the muscle. In a future dissection they will 

 be observed sinking into the substance of the rectus, supplying 

 it with twigs, and then turning forwards to pierce the sheath 

 a second time. They end on the front of the abdomen as 

 the anterior cutaneous nerves. Midway between the spine and 

 the linea alba they give off the lateral cutaneous branches. 

 They likewise supply offsets to the transversus abdominis 

 and two oblique muscles. Minute arteries accompany these 

 nerves. 



The last thoracic nerve also supplies the oblique and 

 transverse muscles, and in addition it gives a branch to the 

 pyramidalis muscle. Its lateral or iliac branch, however, goes 

 to the skin of the buttock. 



The ilio-hypogastric and ilio-inguinal are the two lowest 

 nerves of the series. They are directed forwards between 

 the internal oblique and the transversus close to the crest of 

 the ilium. 



The ilio-hypogastric is the higher of the two. It gives 

 off an iliac or lateral branch, which pierces the two oblique 

 muscles and then crosses the crest of the ilium to reach the 

 skin of the glutaeal region. The anterior portion of the 

 nerve perforates the internal oblique, a short distance in front 

 of the anterior superior spine of the ilium, and then runs 

 forwards towards the linea alba. It does not enter the 

 sheath of the rectus, but becomes superficial by piercing the 

 aponeurosis of the external oblique immediately above the 

 subcutaneous inguinal ring. 



The ilio-inguinal nerve gives off no lateral branch. It 

 pierces the internal oblique, to which it gives branches, a 

 short distance above the inguinal ligament, and it becomes 

 superficial by passing through the subcutaneous inguinal ring. 



