PELVIS MINOR 



439 



is a pararectal fossa, and each lateral part of the wall of the 

 lower portion of the gut is supported by the corresponding 

 levator ani muscle (Figs. 196, 204, 205). 



Flexures of the Rectum. The rectum does not take a 

 straight course along the dorsal wall and floor of the pelvis. 



Anal canal (note 

 apposition of it 



M. sphincter ani internus 

 M. sphincter ani externus 



FIG. 206. Frontal section through the whole length of the Anal Canal. 

 (Symington.) 



B. Bladder. 

 V.D. Ductus deferens. 

 S.V. Seminal vesicle. 



R. Terminal portion of the rectum 

 (note the apposition of its an- 

 terior and posterior walls). 



On the contrary, it presents three abrupt lateral bends or 

 flexures, of which, as a rule, two are convex to the right and 

 one to the left. The sharply marked infoldings of the wall of 

 the gut opposite the flexures are the cause of the so-called plica 

 transver sales recti (O.T. rectal valves) in the interior of the 

 gut. The flexures are best marked when the gut is distended, 

 but even when it is empty they are usually quite obvious. 

 The rectum lies between the bladder and prostate in front 

 n-286 



