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ANATOMY AND PHYSIOLOGY 



True pelvis. The piriformis and obturator interims. These 

 muscles arise from the interior of the pelvis and pass out through 

 the sciatic notches the piriformis through the greater notch and 

 the obturator internus through the lesser notch. They are 

 inserted on the great trochanter and act to rotate it outward. 



They are supplied by nerves which are branches of the sacral 

 plexus. 



They are short muscles but thick and very strong. 



The floor of the pelvis consists of two flat muscles on either side, 

 the levator ani and the coccygeus. 



-Sacrum 



pirifonnis 



Coccyx 



Levator ani (di- 

 vided below 

 the "white 

 line") 



Space for obtu- 

 rator internus 



Rectum 

 Prostate 



Symphysis 



Passage for tfu- 

 teal vessels 

 and nerve 



Pirifonnis 



Passage for sci- 

 atic and pu- 

 dic vessels 

 and nerve 



Ischial spine 



Coccygeus 

 CcJlular interval 



Levator ani 



Capsule of pros- 

 tate, arid pu- 

 bo- prostatic 

 ligaments 



FIG. 89. INTERIOR AND FLOOR OF THE TRUE PELVIS. (Morris.) 



The origin is on the interior of the pelvic wall that is, on 

 the pubic bone and the spine of the ischium, and a line of fascia 

 between the two points. Insertion. The muscles meet each 

 other in the median line, being also attached to certain pelvic 

 organs (bladder and rectum in the male; bladder, rectum, and 

 vagina in the female) and to the coccyx. Their action supports 

 the pelvic organs, especially the rectum, and lifts them in various 

 motions of the body, as in respiration. 



Nerves. From sacral nerves. 



Special notes. These two muscles form a concave floor like an inverted 

 dome, which is the pelvic diaphragm. When this dome contracts it rises. 



There are two openings in the pelvic floor for the bladder and rectum, and 

 a third opening in the female pelvis for the vagina. 



