Internal iliac artery

Anterior trunk

The anterior trunk of the internal iliac artery gives off eight branches:

• Superior vesical artery: (a.k.a. patent part of umbilical artery) it is a large branch, which runs medial to the periosteum of the posterior aspect of the pubis. It supplies the bladder and the distal ureter in both sexes, as well as the proximal aspect of the ductus deferens and the seminal vesicles in males.
• Inferior vesical artery (in males): it is sometimes present and arises with the middle rectal artery. It supplies the ductus deferens, the bladder, seminal vesicles and the prostate gland.
• Vaginal artery (in females): it usually replaces the inferior vesical artery in females and arises near the uterine artery.
• Middle rectal artery: it is a small artery, which sometimes arises close to the inferior vesical artery in males.
• Obturator artery: it runs in an anteromedial direction from the anterior trunk on the lateral pelvic wall to the obturator foramen.
• Uterine artery (in females): it is a large artery, which runs inferomedially from the lateral pelvic wall to the broad ligament of the uterus. It is only present in females and arises below the obturator artery.
• Internal pudendal artery: it arises just inferior to the origin of the obturator artery and descends laterally towards the greater sciatic foramen. Within the pelvis, it crosses the piriformis muscle, the inferior gluteal artery and the sacral plexus. In the gluteal region, it curves around the ischial spine before entering the perineum through the lesser sciatic foramen. In the pelvic and gluteal regions, it gives off muscular branches which supply surrounding muscles and nerves.
• Inferior gluteal artery: it is the largest terminal branch of the anterior trunk, supplying both the buttock and the thigh. It travels inferoposteriorly before it passes between the anterior rami of S1 and S2, or S2 and S3, and then travels between the piriformis and ischiococcygeus muscles. It supplies branches to these muscles as well as to the iliococcygeus muscle. Like the internal pudendal artery, it enters the gluteal region through the greater sciatic foramen. It then descends between the greater trochanter and ischial tuberosity to supply the skin of the thigh.

Mnemonic: there is an easy way to remember all these branches! Just learn the mnemonic ' Often My Sexy Underwear Is Inside Pants' It stands for:

• Obturator a.
• Middle rectal a.
• Superior vesical a.
• Uterine a. (female only)
• Inferior gluteal a.
• Inferior vesical a. (often vaginal a. in females)
• internal Pudendal a.

Posterior trunk

The posterior trunk of the internal iliac artery gives off three branches:

• Iliolumbar artery: it runs anterolaterally towards the medial border of the psoas major muscle, where it divides into the lumbar and iliac branches. The lumbar branch supplies the psoas major and quadratus lumborum muscles, whilst the iliac branch supplies the iliacus muscle. Both of these branches anastomose with other arteries. The lumbar branch anastomoses with the fourth lumbar artery and the iliac branch anastomoses with iliac branches of the obturator artery.

• Lateral sacral artery or arteries: there are usually two lateral sacral arteries which branch off from the posterior trunk. If there is a single artery, it usually quickly divides into superior and inferior branches. The superior artery is larger and supplies the sacral vertebrae before exiting the sacrum through the dorsal foramen. It supplies the skin and muscles dorsal to the sacrum. The inferior artery crosses the piriformis and anterior spinal rami of the sacrum obliquely before descending laterally towards the sympathethic trunk. Here, it anastomoses with the superior counterpart and with the medial sacral artery.
• Superior gluteal artery:  it is the largest branch of the internal iliac artery and essentially a continuation of the posterior trunk. It exits the pelvis by the greater sciatic foramen and divides into superficial and deep branches. Within the pelvic region, it supplies the piriformis and obturator internus muscles. The superficial branch supplies the gluteus maximus muscle and the skin over the sacrum. The deep branch supplies the gluteus medius and gluteus minimus muscles.

The superior gluteal artery, inferior gluteal artery and internal pudendal artery sometimes arise directly from the internal iliac artery.

Mnemonic: A quick and easy way to the branches of the posterior trunk is to memorise the mnemonic ' PILS'. It stands for:

• Posterior branch:
• Iliolumbar a.
• Lateral sacral a.
• Superior gluteal a.
  

More details about the internal iliac arteries are provided below:

Test your knowledge on the main arteries of the lower limb with this quiz.