SURFACE ANATOMY OF THE ABDOMEN 1313 



SURFACE ANATOMY OF THE ABDOMEN. 



ikin. The skin of the front of the abdomen is thin. In the male it is often 

 thickly hair-clad, especially toward the lower part of the middle line; in the female 

 the hairs are confined to the pubes. Just below the line of the iliac crest, especially 

 marked in fat subjects, is a shallow groove termed the iliac furrow, while in the 

 site of the inguinal ligament a sharper fold known as the fold of the groin is easily 

 distinguishable. 



After distension of the abdomen from pregnancy or other causes the skin com- 

 monly presents transverse white lines which are quite smooth, being destitute 

 of papillae; these are known as striae gravidarum or striae albicantes. The linea 

 nigra of pregnancy is often seen as a pigmented brown streak in the middle line 

 between the umbilicus and symphysis pubis. 



In the middle line of the front of the abdomen is a shallow furrow which extends 

 from.the junction between the body of the sternum with the xiphoid process to a 

 short distance below the umbilicus; it corresponds to the linea alba. The umbilicus 

 is situated in the middle line, but it varies in position as regards its height; in an 

 adult subject it is always placed above the middle point of the body, and in a nor- 

 mal well-nourished subject is from 2 to 2.5 cm. above the level of the tubercles 

 of the iliac crests. 



Bones. The bones in relation with the surface of the abdomen are (1) the lower 

 part of the vertebral column and the lower ribs and (2) the pelvis; the former 

 have already been described (page 1303), the latter will be considered with the 

 lower limb. 



Muscles (Fig. 1219). The only muscles of the abdomen which have any consider- 

 able influence on surface form are the Obliquus externus and the Rectus. The 

 upper digitations of origin of Obliquus externus are well-marked in a muscular sub- 

 ject, interdigitating with those of Serratus anterior; the lower digitations are cov- 

 ered by the border of Latissimus dorsi and are not visible. The attachment of the 

 Obliqui externus and internus to the crest of the ilium forms a thick oblique roll 

 which determines the iliac furrow. Sometimes on the front of the lateral region of 

 the abdomen an undulating line marks the passing of the muscular fibers of the 

 Obliquus externus into its aponeurosis. The lateral margin of the Obliquus externus 

 is separated from that of the Latissimus dorsi by a small triangular interval the 

 lumbar triangle the base of which is formed by the iliac crest, and its floor by 

 Obliquus internus. 



The lateral margin of Rectus abdominis is indicated by the linea semilunaris, 

 which may be exactly defined by putting the muscle into action. The surface of 

 the Rectus presents three transverse furrows, the tendinous inscriptions : the upper 

 two of these, viz., one opposite, or a little below, the tip of the xiphoid process, 

 and the other midway between this point and the umbilicus, are usually well- 

 marked; the third, opposite the umbilicus, is not so distinct. Between the two 

 Recti the linea alba can be palpated from the xiphoid process to a point just below 

 the umbilicus; it is represented by a distinct dip between the muscles: beyond 

 this the muscles are in apposition. 



Vessels. In thin subjects the pulsation of the abdominal aorta can be readily 

 felt by making deep pressure in the middle line above the umbilicus. 



Viscera. Under normal conditions the various portions of the digestive tube 

 cannot be identified by simple palpation. Peristalsis of the coils of small intestine 

 can be observed in some persons with extremely thin abdominal walls when some 

 degree of constipation exists. In cases of constipation it is sometimes possible to 

 trace portions of the great intestine by feeling the fecal masses within the gut. 

 In thin persons with relaxed abdominal walls the iliac colon can be felt in the left 

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