548 A MANUAL OF ANATOMY. 



The Posterior Division of the Internal Iliac Artery. 

 (a) The iliolumbar artery. This passes outward and 

 upward beneath the common iliac vessels and psoas magnus 

 muscle, where it divides into two main trunks, the upper 

 and lower, which supply the adjoining parts and anastomose 

 with the last lumbar, gluteal, and deep circumflex iliac 

 arteries. (U) The two lateral sacral pass inward across the 

 sacrum to anastomose with the sacra media, to supply the 

 surrounding parts, and, penetrating the sacral foramina, to be 

 distributed to the posterior sacral region, (c) The gluteal. 

 This is the direct continuation of the posterior trunk, It 

 leaves the pelvic cavity with the superior gluteal nerve 

 through the great sacrosciatic foramen above the pyriformis 

 muscle. For its distribution, see page 612. 



The Internal Iliac Vein 



Is formed at the great sacrosciatic foramen by the junc- 

 tion of the gluteal, sciatic, and internal pudic veins. The 

 venous trunk then ascends and joins the external iliac vein 

 at the sacro-iliac articulation to form the common iliac vein. 

 Besides the above veins the internal iliac receives the lateral 

 sacral, iliolumbar, obturator, prostatic, vesical, hemor- 

 rhoidal (vaginal and uterine in the female) veins. 



DISSECTION. 



Close to the bladder divide the remaining ligaments, vessels, nerves, ure- 

 ters, and vasa deferentia passing to it. 



Remove the bladder and open it from its apex along its anterior wall to the 

 urethra, and this also for its entire length along the upper surface. 



The Openings of the Ureters. 



These openings are three-fourths of an inch behind the 

 internal urinary meatus and the same distance apart. 



The beginning- of the urethra is called the internal 

 meatus. This opening lies in the median line, three-fourths 



