THE MUSCLES AND FASCIA OF THE TRUNK 145 



tilage, one between the ensiform and the umbilicus, 

 and one opposite or below the umbilicus. 



Actions of the Abdominal Muscles. When the thorax 

 and pelvis are fixed these muscles acting together 

 constrict the abdominal cavity, and raising the intra- 

 abdominal pressure also assisted by the diaphragm 

 aid in expelling the fetus from the uterus, feces from 

 the rectum, urine from the bladder. 



The Posterior Muscles of Abdomen (Iliac Region) 



The iliac fascia covers the iliopsoas muscle, within 

 the back part of the abdominal cavity stretched from 

 the iliac crest to the iliac portion of the iliopectineal 

 line. Below it passes beneath the femoral vessels, 

 forming the hinder part of the femoral sheath; outside 

 the vessels it unites with the transversalis fascia at 

 Poupart's ligament. 



Quadratus Lumborum. A quadrilateral muscle 

 placed between the last rib and the pelvis. Origin, 

 iliolumbar ligament, external lip of the crest of the 

 ilium for two inches, from two, three, or four lumbar 

 transverse processes by fleshy slips passing up ante- 

 riorly; insertion, inner half of last rib and upper four 

 lumbar transverse processes. 



Nerves. Last dorsal and upper lumbar. 



Actions. Lateral flexion of both may extend the 

 spine. Draws down the last rib, giving fixed point 

 for the diaphragm, and aids inspiration. Fixed above, 

 draws pelvis to one side, or both draw it forward. 



ILIOPSOAS. It has a broad outer head, iliacus, and 

 a narrow inner head, psoas magnus. 



Iliacus. Origin, upper half of the iliac fossa down 

 as far as the anterior inferior spine, posteriorly from 

 ala of the sacroiliac and iliolumbar ligaments. In- 

 serted mostly into tendon of the psoas; outermost 

 fibers pass to the femur in front of and below the small 

 trochanter. 

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