Course and Topography
The internal iliac artery originates at the bifurcation of the common iliac artery. It then courses inferiorly, entering the lesser pelvis, and descends to the upper margin of the greater sciatic foramen (foramen ischiadicum majus). At this level, the vessel typically divides into its two main divisions: the anterior trunk, which predominantly gives off visceral branches to the pelvic organs, and the posterior trunk, which supplies parietal structures (muscles and fascia of the pelvic wall). Classical anatomy describes this specific bifurcation, although anatomical variations in branching patterns are common.
Branches of the Anterior Trunk (Visceral and Parietal)
The anterior trunk supplies the pelvic viscera, genitalia, and perineum. Its key branches include:
- Umbilical artery (a. umbilicalis) — in adults, its proximal part remains patent and gives rise to the superior vesical arteries (aa. vesicales superiores). The distal segment obliterates to form the medial umbilical ligament.
- Inferior vesical artery (a. vesicalis inferior) — supplies the base of the bladder, prostate, and seminal vesicles in males. In females, its territory is largely supplied by vaginal or uterine artery branches.
- Middle rectal artery (a. rectalis media) — supplies the muscular coat and mucosa of the middle and lower rectum, anastomosing with the superior and inferior rectal arteries.
- Uterine artery (a. uterina) — a vital vessel in the female pelvis. It runs within the base of the broad ligament, crosses superior to the ureter, and supplies the uterus, vagina, fallopian tubes, and ovaries (anastomosing with the a. ovarica).
- Vaginal artery (a. vaginalis) — supplies the vaginal walls and cervix.
- Internal pudendal artery (a. pudenda interna) — a major vessel that exits the pelvis through the infrapiriform foramen (foramen infrapiriforme), hooks around the ischial spine, and re-enters the pelvis through the lesser sciatic foramen. It travels through the pudendal canal (Alcock's canal), giving off inferior rectal, perineal, and the deep and dorsal arteries of the penis or clitoris.
- Obturator artery (a. obturatoria) — runs along the lateral pelvic wall to the obturator canal. It gives off pubic, anterior, and posterior branches. The posterior branch gives rise to the acetabular branch (r. acetabularis), which supplies the hip joint via the ligament of the head of the femur.
Branches of the Posterior Trunk (Parietal)
The posterior trunk supplies the musculoskeletal and fascial structures of the posterior pelvic wall and lower back. It includes:
- Iliolumbar artery (a. iliolumbalis) — divides into lumbar and iliac branches, supplying the psoas major, quadratus lumborum, and iliacus muscles.
- Lateral sacral arteries (aa. sacrales laterales) — descend along the anterior surface of the sacrum, sending branches through the pelvic sacral foramina to supply the spinal meninges, nerve roots, and erector spinae muscles.
- Superior gluteal artery (a. glutea superior) — the largest branch of the posterior trunk. It exits the pelvis through the suprapiriform foramen (foramen suprapiriforme). Its superficial and deep branches supply the gluteus maximus, medius, and minimus muscles.
- Inferior gluteal artery (a. glutea inferior) — exits through the infrapiriform foramen inferior to the piriformis muscle. It gives off the companion artery to the sciatic nerve (a. comitans n. ischiadici) and supplies the posterior hip and thigh muscles.
Important Anastomoses and Clinical Significance
The internal iliac artery system forms numerous vital anastomotic networks critical for surgery and trauma management:
- Corona mortis: An abnormal or normal vascular connection between the obturator branch of the internal iliac (or inferior epigastric) and the external iliac system across the superior pubic ramus. Laceration during pelvic fractures or groin hernia repairs can lead to severe, life-threatening hemorrhage.
- Ureter and Uterine Artery Crossing: During gynecological procedures (such as hysterectomy), surgeons must remember that the ureter passes directly inferior to the uterine artery, carrying a high risk of accidental ligation.
- Gluteal and Cruciate Anastomoses: Rich anastomotic networks connect the superior and inferior gluteal arteries with branches of the femoral circumflex arteries, providing collateral circulation around the hip joint.