The Abdominal Muscles. 

 ] Linea alba 



273 



Vagina ni. recti abdomin: 

 (anterior leaf) 



^. 



Funiculus sperruaticus ^ 



Vagina m. recti 



abdominis (anteritJ 



leaf) (reflected) 



M. pyranjidalis 



__.Fibrae inter- 

 crurales 



Aiinulus inguinalis 

 subcutaneus 



Ligamentuni inguinale 

 reflexum [Collesi] 



Crus inferius 



Crus superius 



I.iganientum suspensoriuni penis 



318. Mm. pyramid ales, viewed from in front. 



(The anterior leaf of the sheath of the rectus has* been partially dissected off and reflected.) 



II. obliqiius externus abdominis (see also Figs. 31fi, 317, 329 and 331). Form: 

 tiat, i-[uadrangnlar, broad, much longer in front than behind. Position: on the anterior and 

 lateral surface of the abdominal and inferior thoracic region. Origin: by 8 fleshy digitations 

 from the outer surface of the 5*11 12'^ rib; the uppermost digitation is usually covered by the 

 pars abdominalis m. pectoralis majoris (see Fig. 319); the 5 upper digitations are inserted between 

 the digitations of the ra. serratus anterior; the 3 lower between those of the m. latissimus dorsi. 

 Insertion: the upper fibers run more transversely, the lower more obliquely, forward and 

 downward. The largest, upper part goes over medianward into a broad, tendinous sheath 

 which runs in front of the m. rectus abdominis and helps to form the anterior leaf of the 

 vagina m. recti abdominis (see p. 279); the next lower muscle bundles pass obliquely to tho 

 /i;/amcntum inguinale [Pouparti] (0. T. Pouparfs ligament) (see p. 280) and leave medianward 

 an open space (annuliis inguinalis sithcntanciis) (see p. 280) for the passage of the funiculus 

 spermaticus; the muscle fibers arising farthest back are attached in fleshy masses to the external 

 lip of the ihac crest. Action: it draws the thorax downward, bends the spinal column forward 

 and toward the same side and rotates it toward the other side; when the thorax is fixed it 

 elevates the pelvis. Innervation: rami anteriores [nn. intercostales] of the nn. thora- 

 cales Till XII and the nn. iliohypogastricus and ilioinguinalis. 



M. pyramid.ilis, inconstant. Form: flat, oblong-triangular. Position: close to the 

 median plane above the symphysis pubis, in front of the m. rectus abdominis, in a duplicaturo 

 of the anterior leaf of the vagina m. recti abdominis. Origin: anterior surface of the ramus 

 superior ossis pubis and of the symphysis ossium pubis. Insertion: the fibers run upward 

 and medianward to the hnea alba. Action: it tightens the linea alba in the upright position 

 and gives rise to the median groove below the navel when the abdominal muscles are relaxed. 

 Innervation: r. anterior [n. intercostalisj of the n. thoracalis XII. 



