280 



PRACTICAL ANATOMY. 



branch of the internal iliac artery. Find- the groove* between this muscle and 

 the psoas, containing the anterior crural nerve. 



Dissection of Sacral Plexus (Figs. 193 and 194). Cut through the symphysis 

 pubis and pull outward on both pubic bones, and separate the ilium from the 

 sacrum, at the sacro-iliac synchondrosis. Then study the following points : 



1. The plexus is located on the posterior pelvic wall. 



2. It rests on the pyriformis muscle. 



FROM LAST THORACIC 



CENITO-CR URA L 



ILIO-HYPOGASTRIC 



ILIO-INOl'INAL 



EXTERN A L 

 CUTANEOUS 



OBTURATOR 



AIY'ESSORY 



ui:ri-RATOR 



BRANCH TO ILIACUS 

 ANTERIOR CRURAL 



SUPERIOR G LUTE A L 

 INFERIOR GLUTEAL 



ORE A T SCI A TIC 



KKRVE TO 



QUADRA TVS 



FEMORIS 



EXTERNAL 



POPLITEAL 



SECTION 



INTERNAL 



POPLITEAL 



>/ :< T/O.V 



TO HAMSTRINGS 



FIRST LUMISAR 



SECOND LUMIiA R 



THIRD LUMBAR 



-7 FOUR Til L UMIiA R 



FIFTH LUMBAR 



FIRST SACRAL 



SECOND SACRAL 



THIRD SACRAL 



PX8CBRAL 



FHUHTII SACRAL 



PKRFORA TING 

 CUTANEOUS 



/'/././.V.K.I/, 

 FIFTH SACRAL 

 JfEKVK TO COCCY'iKrS 



HER VE TOLE\ 'A T(,R 

 A XI 



FIRST COCCYGEAL 



VISCERAL 



SMALL SCIA TIC PUDIC 



NERVE TO OBTURATOR INTERNUS 



FIG. 193. DIAGRAM OF THE LUMBAR AND SACRAL PLEXUSES. Modified from Paterson. 



3. It is covered by the pelvic fascia and peritoneum. 



4. It is crossed by the internal iliac vessels. 



5. The gluteal and sciatic arteries transfix it. 



6. It receives the fifth and part of the fourth lumbar nerves. 



7. The part received from the lumbar is called the litmbo-sacral cord. 



8. The sacra/ plexus is formed by the union of the lumbo-sacral cord and 

 the anterior primary divisions of the first, second, third, and a part of the fourth 

 sacral nerves. 



