5b. 2. The External Iliac Artery

(A. Iliaca Externa)

The external iliac artery (Fig. 539) is larger than the hypogastric, and passes obliquely downward and lateralward along the medial border of the Psoas major, from the bifurcation of the common iliac to a point beneath the inguinal ligament, midway between the anterior superior spine of the ilium and the symphysis pubis, where it enters the thigh and becomes the femoral artery. 1 Relations.—In front and medially, the artery is in relation with the peritoneum, subperitoneal areolar tissue, the termination of the ileum and frequently the vermiform process on the right side, and the sigmoid colon on the left, and a thin layer of fascia, derived from the iliac fascia, which surrounds the artery and vein. At its origin it is crossed by the ovarian vessels in the female, and occasionally by the ureter. The internal spermatic vessels lie for some distance upon it near its termination, and it is crossed in this situation by the external spermatic branch of the genitofemoral nerve and the deep iliac circumflex vein; the ductus deferens in the male, and the round ligament of the uterus in the female, curve down across its medial side. Behind, it is in relation with the medial border of the Psoas major, from which it is separated by the iliac fascia. At the upper part of its course, the external iliac vein lies partly behind it, but lower down lies entirely to its medial side. Laterally, it rests against the Psoas major, from which it is separated by the iliac fascia. Numerous lymphatic vessels and lymph glands lie on the front and on the medial side of the vessel. 2 Collateral Circulation.—The principal anastomoses in carrying on the collateral circulation, after the application of a ligature to the external iliac, are: the iliolumbar with the iliac circumflex; the superior gluteal with the lateral femoral circumflex; the obturator with the medial femoral circumflex; the inferior gluteal with the first perforating and circumflex branches of the profunda artery; and the internal pudendal with the external pudendal. When the obturator arises from the inferior epigastric, it is supplied with blood by branches, from either the hypogastric, the lateral sacral, or the internal pudendal. The inferior epigastric receives its supply from the internal mammary and lower intercostal arteries, and from the hypogastric by the anastomoses of its branches with the obturator. 105 3 Branches.—Besides several small branches to the Psoas major and the neighboring lymph glands, the external iliac gives off two branches of considerable size: 4

Inferior Epigastric.

Deep Iliac Circumflex.

The inferior epigastric artery (a. epigastrica inferior; deep epigastric artery) (Fig. 547) arises from the external iliac, immediately above the inguinal ligament. It curves forward in the subperitoneal tissue, and then ascends obliquely along the medial margin of the abdominal inguinal ring; continuing its course upward, it pierces the transversalis fascia, and, passing in front of the linea semicircularis, ascends between the Rectus abdominis and the posterior lamella of its sheath. It finally divides into numerous branches, which anastomose, above the umbilicus, with the superior epigastric branch of the internal mammary and with the lower intercostal arteries (Fig. 522). As the inferior epigastric artery passes obliquely upward from its origin it lies along the lower and medial margins of the abdominal inguinal ring, and behind the commencement of the spermatic cord. The ductus deferens, as it leaves the spermatic cord in the male, and the round ligament of the uterus in the female, winds around the lateral and posterior aspects of the artery. 5 Branches.—The branches of the vessel are: the external spermatic artery (cremasteric artery), which accompanies the spermatic cord, and supplies the Cremaster and other coverings of the cord, anastomosing with the internal spermatic artery (in the female it is very small and accompanies the round ligament); a pubic branch which runs along the inguinal ligament, and then descends along the medial margin of the femoral ring to the back of the pubis, and there anastomoses with the pubic branch of the obturator artery; muscular branches, some of which are distributed to the abdominal muscles and peritoneum, anastomosing with the iliac circumflex and lumbar arteries; branches which perforate the tendon of the Obliquus externus, and supply the integument, anastomosing with branches of the superficial epigastric. 6 10

Peculiarities.—The origin of the inferior epigastric may take place from any part of the external iliac between the inguinal ligament and a point 6 cm. above it; or it may arise below this ligament, from the femoral. It frequently springs from the external iliac, by a common trunk with the obturator. Sometimes it arises from the obturator, the latter vessel being furnished by the hypogastric, or it may be formed of two branches, one derived from the external iliac, the other from the hypogastric. 7 The deep iliac circumflex artery (a. circumflexa ilium profunda) arises from the lateral aspect of the external iliac nearly opposite the inferior epigastric artery. It ascends obliquely lateralward behind the inguinal ligament, contained in a fibrous sheath formed by the junction of the transversalis fascia and iliac fascia, to the anterior superior iliac spine, where it anastomoses with the ascending branch of the lateral femoral circumflex artery. It then pierces the transversalis fascia and passes along the inner lip of the crest of the ilium to about its middle, where it perforates the Transversus, and runs backward between that muscle and the Obliquus internus, to anastomose with the iliolumbar and superior gluteal arteries. Opposite the anterior superior spine of the ilium it gives off a large branch, which ascends between the Obliquus internus and Transversus muscles, supplying them, and anastomosing with the lumbar and inferior epigastric arteries. 8

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