37 6 



APPLIED ANATOMY. 



exposed, but, as they rapidly approximate each other below, an incision usually 

 passes either through the edge of one muscle or, if it passes exactly between them, 

 may expose the edges of both. 



The lateral edge of the sheath is formed primarily by the splitting of the tendon 

 of the internal oblique muscle, one part going in front and the other behind the 

 muscle. The tendon of the external oblique blends with the anterior layer of the 

 tendon of the internal oblique a little to the medial side of the edge of the rectus, 

 and as the pubes is approached the external oblique has its attachment nearer and 

 nearer to the linea alba, so that close to the pubes the external oblique is separated 

 from the internal oblique and goes to form the internal pillar of the external ring and 

 has the conjoined tendon behind it (Fig. 388). 



The tendon of the transversalis blends with the posterior layer of the internal 

 oblique tendon until the lower fourth of the rectus is reached, when they both pass 

 .in front of the rectus to form the conjoined tendon. The medial portion of the 



Sheath of the rectus 



Rectus abdominis 



External oblique 

 Internal oblique 

 Transversalis 



External oblique 

 Internal oblique 

 Transversalis 



Spine of pubis 

 Crest of pubis 



FIG. 388. Sheath of the rectus abdominis muscle. 



sheath of the rectus is attached to the symphysis and crest of the pubis ; its lateral 

 portion, forming the conjoined tendon, is attached from the spine of the pubis along 

 the iliopectineal line for the distance of 4 cm. (i/^ in.). It lies behind the external 

 abdominal ring. 



The lower edge of the posterior portion of the sheath of the rectus is called the 

 semilunar fold of Douglas; the deep epigastric artery ascends beneath this fold about 

 its middle, or a little to its outer side. From this arrangement it will be seen that 

 an incision over or near the lateral edge of the rectus below the umbilicus will pass 

 through two aponeurotic layers, viz. , the external oblique and the blended tendons 

 of the internal oblique and transversalis (Fig. 388). 



If it is desired to examine the rectus muscle, its sheath can be opened at its 

 edge and the muscle lifted up from the posterior layer, but it cannot be detached 

 from the anterior layer above the umbilicus unless dissected loose from the lineae 

 transversae. 



