ABDOMINAL MUSCLES 



301 



Abdominal Muscles 



The obliquus abdominis externus is somewhat thinner and has a less extensive 

 origin, which begins at the lower part of the fifth intercostal space and ends on 

 the last rib above its middle. The direction of the fibers in the flank is horizontal, 

 and they do not reach to the external angle of the ilium, nor as high as the lumbar 

 transverse processes. (In this region the abdominal tunic has a strong attachment 

 to the point of the hip and the lumbo-dorsal fascia.) The aponeurosis is intimately 

 united with the abdominal tunic, and does not detach a layer on the inner surface 

 of the thigh. 



The obliquus abdominis internus is more developed and has an additional 



Fig. 211 — Deeper Muscles of Neck, Shoulder, .\nd Thorax of Ox. 

 c', Cleido-occipitalis muscle; d, sterno-cephalicus; /, /', long and external heads -of triceps; g, superficial 

 pectoral muscle; h, h', posterior and anterior deep pectoral muscles; /, i', serratus magnus; k, latissimus dorsi; 

 i, obliquus abdominis externus; i', bicejjs brachii; w, splenius; x, rhomboideus; y, trachelo-mastoideus; z, 

 supraspinatus; z', infraspinatus; z" , tenilon of insertion of z" ; 1' , cartilage of scajjula; 2, tuberosity of spine of 

 scapula; 3, acromion; 5, external tuberosity of humerus; 6, deltoid tuberosity; 8, olecranon; 26, transverse 

 processes of cervical vertebrae; 27 , posterior auricular muscles; X , wing of atlas. (After EUenberger-Baum, 

 Anat. fur Kiinstler.) 



origin from the lumbo-dorsal fascia. The aponeurosis blends with that of the 

 external oblique near the linea alba, and detaches a layer which assists in the for- 

 mation of the internal sheath of the rectus. 



The rectus abdominis arises on the lateral border of the sternum as far 

 forward as the third costal cartilage. The two muscles are separated, except 

 near the pelvis, by an interval varying from two to four inches (ca. 5 to 

 10 cm.), so that this part of the abdominal wall is entirely fibrous. (The 

 umbilicus is in a transverse plane through the third lumbar vertebra.) There 

 are five tendinous inscriptions, on the third of which is a foramen for the 

 passage of the subcutaneous abdominal vein (milk vein). The prepubic 

 tendon has, in addition to branches inserted into the ilio-pectineal eminences, 

 a strong attachment to the median common tendon of the adductors of the 

 thigh, so that the abdominal wall is strongly retracted and almost vertical at 

 its junction with the pelvis. 



