680 THE VASCULAR SYSTEMS 



The anastomotic artery is directed downward across the External rotators and 

 assists in forming the so-called crucial anastomosis by anastomosing with the 

 superior perforating and the internal and external circumflex arteries. 



The articular branch, generally derived from the anastomotic, is distributed to 

 the capsule of the hip-joint. 



The cutaneous branches are distributed to the skin of the buttock and back of 

 ihe thigh. 



The iliolumbar artery (a. iliolumbalis), given off from the posterior trunk of 

 the internal iliac, turns upward and outward between the obturator nerve and 

 lumbosacral cord, to the inner margin of the Psoas muscle, behind which it divides 

 into a lumbar and an iliac branch. 



The lumbar branch (ramus lumbalis) supplies the Psoas and Quadratus lum- 

 borum muscles, anastomosing with the last lumbar artery, and sends a small 

 spinal branch (ramus spinalis) through the intervertebral foramen, between the 

 last lumbar vertebra and the sacrum, into the vertebral canal, to supply the 

 cauda equina. 



The iliac branch (ramus iliacus) descends to supply the Iliacus muscle; some 

 offshoots, running between the muscle and the bone, anastomose with the iliac 

 branch of the obturator; one of these enters an oblique canal to supply the diploe, 

 while others run along the crest of the ilium, distributing branches to the Gluteal 

 and Abdominal muscles, and anastomose in their course with the gluteal circum- 

 flex iliac, and external circumflex arteries. 



The lateral sacral arteries (a. sacralis lateralis) (Fig. 473) are usually two 

 in number superior and inferior. 



The superior, which is of large size, passes inward, and, after anastomosing 

 with branches from the middle sacral, enters the first or second anterior sacral 

 , fora men, supplies branches to the contents of the sacral canal, and, escaping by 

 the corresponding posterior sacral foramen^ is distributed to the skin and muscles 

 on the dorsum of the sacrum, anastomosing with the gluteal. 



The inferior passes obliquely across the front of the Pyriformis muscle and 

 sacral nerves to the inner side of the anterior sacral foramina, descends on the 

 front of the sacrum, and anastomoses over the coccyx with the middle sacral and 

 opposite lateral sacral artery. In its course it gives off branches which enter the 

 anterior sacral foramina (rami spinales) ; these, after supplying the contents of the 

 sacral canal, escape by the posterior sacral foramina, and are distributed to the 

 muscles and skin on the dorsal surface of the sacrum, anastomosing with the gluteai. 



The gluteal artery (a. glutaea superior} (Fig. 477) is the largest branch of 

 the internal iliac, and appears to be the continuation of the posterior division of 

 that vessel. It is a short, thick trunk which runs backward between the lumbo- 

 sacral cord and the first sacral nerve, and, passing out of the pelvis above the 

 upper border of the Pyriformis muscle, immediately divides into a superficial 

 and a deep branch. Within the pelvis it gives off a few muscular branches to the 

 Iliacus, Pyriformis, and Obturator internus, and, just previous to emerging from 

 that cavity, a nutrient artery which enters the ilium. 



The superficial branch enters the deep surface of the Gluteus maximus, and 

 divides into numerous branches, some of which supply the muscle, while others per- 

 forate its tendinous origin, and supply the integument covering the posterior sur- 

 face of the sacrum, anastomosing with the posterior branches of the sacral arteries. 



The deep branch lies under the Gluteus medius and almost immediately sub- 

 divides into two. Of these, the superior division (ramus superior), continuing the 

 original course of the vessel, passes along the upper border of the Gluteus mini- 

 mus to the anterior superior spine of the ilium, anastomosing with the circumflex 

 iliac and ascending branches of the external circumflex artery. The inferior 

 divisiqn (ramus inferior) crosses the Gluteus minimus obliquely to the trochanter 



