940 THE VASCULAK SYSTEM. 



its upper margin, to the obturator foramen, through the upper part of which it 

 passes. It terminates, immediately on entering the thigh, by dividing into anterior 

 and posterior terminal branches, which skirt round the margin of the obturator 

 foramen deep to the obturator externus muscle. It is accompanied, in the whole 

 of its course, by the obturator nerve and vein, the nerve being above the artery 

 and the vein below it. 



To its lateral side is the pelvic fascia, which intervenes between it and the upper 

 part of the obturator internus muscle, whilst on its medial side it is covered by 

 peritoneum. The ureter intervenes between the posterior part of the artery and 

 the peritoneum. When the bladder is distended it also comes into close relation 

 with the lower and anterior part of the artery. In the female the ovarian vessels 

 and the broad ligament form the medial relations of the obturator artery. 



Branches. All the branches except the terminal are given off before the artery 

 leaves the pelvis. They include : (a) Muscular branches to the obturator internus, 

 levator aui and ilio-psoas muscles. (6) A nutrient branch to the ilium, which passes 

 deep to the ilio-psoas muscle, supplies the bone, and anastomoses with the ilio-lumbar 

 artery, (c) A vesical branch or branches pass medially to the bladder beneath the 

 lateral false ligament, (d) A pubic branch ascends on the posterior surface of the pubis, 

 and anastomoses with its fellow of the opposite side and with the pubic branch of the 

 inferior epigastric. It is given off just before the artery leaves the pelvis, and, in its 

 upward course, it may pass either on the lateral or medial side of the external iliac vein, 

 whilst not infrequently it runs on the medial side of the femoral ring. In the latter 

 case it is important in relation to femoral hernia ; this importance is emphasised when, 

 as sometimes happens, the obturator artery arises as an enlarged pubic branch of 

 the inferior epigastric artery instead of from the hypogastric. (e) Terminal. The 

 anterior terminal branch runs forwards, and the posterior backwards around the margin 

 of the obturator foramen. They lie on the obturator membrane, under cover of 

 the obturator externus, and they anastomose together at the lower margin of the 

 foramen. Both give off offsets which anastomose with the medial circumflex artery, 

 and twigs of supply to the adjacent muscles. The posterior branch also gives an 

 acetabular branch to the hip-joint, which passes upwards, through the acetabular notch 

 on the medial side of the transverse ligament, to supply the ligamentum teres and the 

 head of the femur. 



2. Arteria Pudenda Interna. The internal pudendal artery (Figs. 774 

 and 775) arises from the anterior division of the hypogastric, close to the origin 

 of the. inferior glutaeal artery, which slightly exceeds it in size. It runs downwards 

 and backwards, to the lower part of the greater sciatic foramen, lying anterior to 

 the piriformis muscle and the sacral plexus, from both of which it is separated by 

 the pelvic fascia. At the lower border of the piriformis it pierces the pelvic 

 fascia, passes between the piriformis and coccygeus muscles, and leaves the pelvis 

 to enter the buttock. It is accompanied by venae comites, the inferior gluteal 

 vessels and nerves, the pudendal nerve, and the nerve to the obturator internus. ; 

 In the buttock it lies on the spine of the ischium, under cover of the glutseus; 

 maximus, and between the pudendal nerve and the nerve to the obturator in- 

 ternus, the former being' medial to it. It next passes through the lesser sciatic 

 foramen and enters the perineum, in the anterior part of which it terminates by 

 dividing into the profunda artery of the penis and the dorsal artery of the penis. 



In the first part of its course in the perineum the artery lies in the lateral 

 fascial wall of the ischio-rectal fossa, where it is enclosed in a canal in the fascia 

 (Alcock's canal). This canal, which is situated about one and a half inches above th< 

 lower margin of the tuberosity of the ischium, contains also the pudendal veint 

 and the terminal parts of the pudendal nerve, viz., the dorsal nerve of the penis 

 which lies above the artery, and the perineal division, which lies below the vessel 

 From the ischio-rectal fossa the internal pudendal artery is continued forward; 

 between the two layers of the fascia of the urogenital diaphragm (O.T. triangula 

 ligament of the urethra), and close to the ramus of the pubis. About half-an 

 inch below the arcuate ligament it turns somewhat abruptly forwards, pierces th 1 

 inferior fascia of the urogenital diaphragm, and immediately divides into it 

 terminal branches, viz., the profunda artery and the dorsal artery of the 



