The Abdominal Muscles. 279 



M. traiisversus abdominis (see also Figs. 313, 321 and 332). Form: flat, quadrangular, 

 broad, much longer in front than behind. Position: on the anterior and lateral surface of 

 the abdomen, completely covered by the mm. obliqui abdominis, partly also by the m. rectus 

 abdominis. Origin: from the Lntemal surface of the 6tii 12*1^ costal cartilage, fi'om the union 

 of the two leaves of the fascia lumbodorsalis (see Figs. 332 and 333), from the internal lip 

 of the iliac crest and from the lateral two thirds of the hg. inguinale. Insertion: the fibers 

 are paraleU, run transversely forward and go over into a tendon plate along a line which is 

 concave medianward (Ihiea semihmaris [SpigeU]). This tendon plate (see also Figs. 322 

 and 323) runs, in its upper two thirds, behind the m. rectus abdominis and strengthens the 

 posterior leaf of the sheath of the rectus; in the lower third, where there is no posterior leaf 

 of the rectal sheath, it goes in front of the m. rectus abdominis and fuses with the anterior 

 leaf of the rectal sheath. The lowermost fibers arch downward and help to form the posterior 

 wall of the inguinal canal (see pag. 282); they are attached partly to the upper surface of 

 the pubis, partly to the hg. inguinale. Action: it pulls the ribs downward and diminishes 

 the size of the abdominal cavity. Innervation: rami anteriores [nn. intercostales] of the 

 nn. thoracales VII XII as well as the nn. Oiohypogastricus and ilioinguinalis. 



Vagina m. recti abdominis (sheath of the rectus) (see also Figs. 317, 319, 320, 

 322 and 323) consists on each side of two broad tendinous leaves, which cover, dii'ectly, the 

 anterior and posterior surfaces of the m. rectus abdominis and which are formed by the tendons 

 of the mm. obliqui et transversus abdominis; medianward both leaves meet those of the other 

 side in the linea alba. The anterior leaf covers the whole anterior surface of the m. rectus 

 and is firmly fased with its inscriptiones tendineae. It is very thin above and there serves 

 to give origin to the pars abdominalis of the m. pectoralis major; it becomes stronger lower 

 down and consists of interwoven fibers. In its upper two thirds it is fonned by the anterior 

 leaf of the tendon of the m. obliquus Latemus, with which is fused the tendon of the m. obliquus 

 externus (see Fig. 322), in its lower third by the union of the tendons of the mm. obUqui 

 and of the mm. transversus abdominis (see Fig. 323). The posterior leaf is much shorter, 

 begins on the costal cartilages at the angulus infi-astemalis and ends, more or less sharply, 

 somewhat below the navel in a margin, the H7iea semicircularis [ Douglasi] , which is concave 

 below and stretches out lateralward from the linea alba ; it consists of the transverse tendinous 

 fibers of the posterior leaf of the tendon of the m. obhquus internus abdominis and those of 

 the m. transversus abdominis. 



Linea alba (see also Figs. 317, 318 and 321 323) is a tough connective tissue strip 

 which extends in the median plane between the mm. recti abdominis fi'om the proc. xj'phoideus 

 ( to the symphysis ossiimi pubis. Below the proc. xyphoideus it gi-aduaUy broadens, being 

 about twice as wide at the level of the navel as it is higher up, and again narrows below 

 the navel to a thin cord whicJi is attached behind the tendons of the mm. recti abdominis 

 to the hg. pubicum superius by means of a triangular expansion (adminiculum lineae albae) 

 (see Fig. 328). The sheath of the rectus is attached to the linea alba; indeed it forms it, in 

 a way, through the imion of the two leaves of the right side with the two leaves of the left. 

 Approximately in its middle and about at the level of the body of the 4'ii lumbar vertebra the 

 linea alba contains the navel, umbilicus. 



Ligamentum fundiforme penis (0. T. suspensory ligament) (see Figs. 316 and 317) 

 (in the male) is a broad band, consisting essentially of elastic fibers; it arises, above the 

 symphysis ossium pubis, from the anterior surface of the vagina m. recti and the hnea alba 

 as weU as from the fascia supei-ficiahs abdominis. It surrounds the penis like a loop by 

 means of its two Umbs and often radiates out into the scrotum. 



Ligamentum fundiforme clitoridis (0. T. suspensory ligament) (see also Fig. 675) 

 (in the female) corresponds to the ligament just mentioned in the male. 



