526 



HUMAN ANATOMY. 



into three areas or foveae (Fig. 532). The median of these foveae lies between the 

 urachus and the lateral umbilical fold and forms the supravesical fossa, having for 

 its floor the rectus muscle. Between the lateral umbilical and the epigastric folds 

 is the hiner inguinal fossa, having for its floor the conjoined tendon, and being 

 therefore the region in which direct inguinal hernias arise ; and lateral to the epi- 



FiG. 532. 



Peritoneal surface 



Plica epigastrica 



Hesselbach's triangle. 

 Vas deferens 



External iliac artery 

 External iliac vein 



Plica hypogastrica. 



Outer edge of rectus 

 muscle 



Supravesical fossa 



Outer inguinal fossa 

 Inner inguinal fossa 



Bladder, somewhat 

 distended 



Median umbilical ligament 



Posterior surface of anterior abdominal wall of formalin subject. 



gastric fold is the outer inguinal fossa, in whose floor is found the internal abdominal 

 ring, just to the outer side of the deep epigastric artery. 



The triangular area bounded by Poupart's ligament below, the lateral edge of 

 the rectus muscle medially, and the plica epigastrica laterally has been termed the 

 triangle of Hesselbach. It is almost identical with the middle inguinal fossa, and 

 defines a little more precisely the seat of the direct hernias. 



(f) THE HYPOSKELETAL MUSCLES. 



It seems probable that the psoas major and the psoas minor muscles are, in part 

 at least, assignable to the group of abdominal hyposkeletal niuscles. The close 

 association of the psoas major with the iliacus and its attachment to the femur make it 

 convenient, however, to defer their description until later (page 623). 



PRACTICAL CONSIDERATIONS. 



THE ABDOMEN. 



The abdominal cavity is bounded above by the diaphragm ; below by the floor 

 of the pelvis ; laterally by the diaphragm, the lower ribs, the abdominal muscles, and 

 the lateral expansions of the ilia ; posteriorly by the diaphragm^ the tenth, eleventh, 

 and twelfth ribs, the lumbar muscles and vertebrae, the posterior portions of the ilia, 

 and the ischial, sacral, coccygeal, and pubic bones ; and inferiorly by the levatores 

 ani and coccygei muscles. It should be noted that the roof, the floor, and much of 

 the remaining parietes of the abdomen are made up of muscular tissue which, by 

 contraction or by relaxation or stretching, can alter the size of the cavity, aftect the 

 relations of the contained viscera, and vary the compression to which they are subject. 

 The tonicity of the muscular walls brings about a normal intra-abdominal pressure 

 which serves in health to retain in position and to give support to the viscera 

 This pressure is increased in inspiration and by straining, lifting, or coughing. I. 

 then, by increasing the outward pressure of the viscera upon the internal sur- 

 face of the parietes, favors the production of hernia, the protrusion of the intestine 



