476 



THE MUSCULAK SYSTEM. 



THE MUSCLES OF THE ABDOMINAL WALL. 



The muscles of the abdominal wall are in three series lateral, anterior, and posterior. 



The lateral muscles of the abdominal wall comprise the obliquus externus 

 abdominis, obliquus internus abdominis, and transversus abdominis. 



M. Obliquus Externus Abdominis. The obliquus externus abdominis is a 

 broad thin sheet of muscle, with an origin from the lateral surfaces of the lower 

 eight ribs, by slips which interdigitate with the serratus anterior and latissimus 



OBLIQUUS EXTERNUS 

 ABDOMINIS' 

 (reflected) 



Spermatic funiculus-- 



Bxternal spermatic 

 fascia' 



.OBLIQUOS EXTERNUS 

 ABDOMINIS 



^ 



* ABDOMINIS 



Anterior superior 

 /'iliac spine 



._ TRANSVERSUS 

 'ABDOMINIS 



\OBLIQUUS INTERNUS 

 ABDOMINIS (reflected) 



Aponeurosis of obliquus 

 "externus (reflected) 

 Abdominal inguinal ring 

 Spermatic fnniculus and 

 infundibuliform fascia 

 Fascia transversalis 



Falx apolfeurotica iu- 

 guinalis 



Fossa ovalis (O.T. saphen- 

 ous opening) 



Great saphenous vein 



FIG. 422. THE DISSECTION OF THE INGUINAL CANAL. 



dorsi muscles. The muscular fibres radiate downwards and forwards, the lowest 

 fibres passing vertically downwards. 



The muscle fibres of the lower and posterior part of the muscle are inserted, 

 directly, into the external lip of the iliac crest in its anterior half or two-thirds 

 (Fig. 369, p. 415). The rest of the muscle fibres are inserted into an extensive 

 triangular aponeurosis which forms part of the anterior abdominal wall. This 

 aponeurosis is broader 'below than above ; it is united with part of the aponeurosis 

 of the obliquus internus in the superior three-fourths of its extent, to form the 

 anterior layer of the sheath of the rectus muscle. It thus gains an attachment, 

 above to the xiphoid process, below to the symphysis pubis, and by its intermediate 

 fibres to the linea alba. 



The linea alba is a band of interlacing fibres, about half an inch in width at its 

 widest part. It occupies the median plane of the anterior abdominal wall in its 

 whole extent, is pierced by the umbilicus (annulus umbilicalis), and forms the 

 greater part of the ultimate insertion of all the lateral abdominal muscles. 



