938 THE VASCULAE SYSTEM. 



circumflex iliac arteries ; it also gives off a spinal branch, which enters the inter- 

 vertebral foramen between the fifth lumbar vertebra and the sacrum, and is dis- 

 tributed like the spinal branches of the lumbar and the aortic intercostal arteries. 



2. Arterise Sacrales Laterales. There is sometimes only a single lateral 

 sacral artery on each side ; more commonly there are two, superior and inferior. 



Both run downwards and medially, on the front of the sacrum. The inferior 

 passes anterior to the piriformis and the sacral nerves, and descends, on the lateral 

 side of the sympathetic trunk, to the coccyx, where it terminates by anastomosing 

 with the middle sacral. The superior branch reaches only as far as the first or the 

 second anterior sacral foramen ; then it enters the sacral canal. It anastomoses 

 with the lower branch and with the middle sacral artery. Branches are given off by 

 the lateral sacral arteries to the piriformis, and to the sacral nerves. Spinal offsets 

 are also given off, which pass through the anterior sacral foramina to the sacral 

 canal ; they supply the membranes of the spinal medulla, the roots of the sacral 

 nerves, and the filum terminale, and anastomose with other spinal arteries. They 

 then pass through the posterior sacral foramina, and anastomose on the back of the 

 sacrum with branches of the superior and inferior glutseal arteries. 



3. Arteria Glutsea Superior (Figs. 774 and 776). After giving off the ilio- 

 lumbar and lateral sacral branches, the posterior division of the hypogastric 

 artery is continued as the superior gluteal artery. This is a large vessel which 

 pierces the pelvic fascia, and passes backwards, between the lumbo-sacral trunk and 

 the first sacral nerve. It leaves the pelvis through the upper part of the greater 

 sciatic foramen, above the piriformis muscle, and enters the buttock, where it 

 divides, under cover of the glutseus maximus and between the adjacent borders of 

 the piriformis and glutseus medius muscles, into superficial and deep branches. 



(a) The superficial branch divides at once into numerous rami, some of which supply 

 the gluteeus maximus, whilst others pass through it, near its origin, to the overlying skin. 

 The branches freely anastomose with branches of the inferior gluteal, internal pudendal, 

 medial circumflex, deep circumflex iliac, and lateral sacral arteries. 



(b) The deep terminal branch, accompanied by the superior gluteal nerve, runs forwards 

 between the glutseus medius and minimus, and, after giving a nutrient branch to the ilium, 

 subdivides into upper and lower branches. The upper branch, runs forwards along 

 the origin of the glutseus minimus from the anterior curved line of the ilium, and 

 passes beyond the anterior margins of the gluteeus medius and minimus to anastomose. 

 under cover of the tensor fasciae latse, with the ascending branch of the lateral circumflex 

 artery. It anastomoses with the deep circumflex iliac artery also, and it supplies musculai 

 branches to the adjacent muscles. The lower branch passes more directly forwards 

 across the glutaeus minimus, towards the trochanter major, along with the branch of the 

 superior gluteal nerve which supplies the tensor fasciae latse. It supplies the glutea 

 muscles, and anastomoses with the ascending branch of the lateral circumflex artery. 



Before leaving the pelvis the gluteal artery gives muscular branches to the pelvi< 

 diaphragm and the obturator internus, small neural branches to the roots of the sacra 

 plexus, and nutrient branches to the hip-bone. 



BRANCHES OF THE ANTERIOR DIVISION. 



The anterior division gives off both parietal and visceral branches, and i 

 continued as the umbilical artery. The parietal branches are the obturator, th< 

 internal pudendal, and the inferior gluteal. The visceral branches include th< 

 superior and inferior vesical, and the middle hsemorrhoidal arteries in the malt 

 In the female the anterior division of the hypogastric artery gives off simila 

 visceral branches, and, in addition, a uterine and a vaginal branch. 



VISCERAL BRANCHES. 



1. Arteria Vesicalis Superior. The superior vesical artery arises from t 

 incompletely obliterated posterior part of the umbilical artery, as it lies at the sid 

 of the bladder. It passes medially to the upper part of the urinary bladder an 

 divides into numerous branches which anastomose with the other vesical arterie 

 and it also gives small branches to the urachus, and often to the lower pai 

 of the ureter. It may in addition give off a middle vesical branch, and nc 

 infrequently the long slender artery to the ductus de/erens arises from it. 



