Vessel Course and Topography
The internal iliac artery originates at the bifurcation of the common iliac artery. It then courses inferiorly, descending into the lesser pelvis until it reaches the superior margin of the greater sciatic foramen (foramen ischiadicum majus). At this level, the vessel typically divides into two main branches. The first is the anterior trunk, which predominantly gives off visceral branches to the internal organs. The second is the posterior trunk, which supplies parietal structures (muscles and fascia). Classical anatomy defines this specific bifurcation, although individual variations in branching patterns do occur in practice.
Branches of the Anterior Trunk (Visceral)
The anterior trunk supplies blood to the urogenital organs and the rectum. Its key branches include:
- Umbilical artery (a. umbilicalis) — in adults, its proximal part remains patent and gives off 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 neck of the urinary bladder, and in males, additionally supplies the prostate and seminal vesicles. In females, this function is frequently assumed by branches of the uterine or vaginal arteries.
- Middle rectal artery (a. rectalis media) — courses toward the ampulla of the rectum, forming anastomoses with the superior and inferior rectal arteries.
- Uterine artery (a. uterina) — a critical vessel of the female pelvis. It runs within the base of the broad ligament of the uterus, crossing the ureter, and supplies branches to the uterus, vagina, uterine tubes, and ovaries (where it anastomoses with the a. ovarica).
- Vaginal artery (a. vaginalis) — courses toward the vaginal fornices and the cervix.
- Internal pudendal artery (a. pudenda interna) — a complex vessel that exits the pelvis through the infrapiriform foramen (foramen infrapiriforme), hooks around the ischial spine, and re-enters through the lesser sciatic foramen. It runs within Alcock's canal, giving off inferior rectal and perineal arteries, as well as the deep and dorsal arteries of the penis or clitoris.
- Obturator artery (a. obturatoria) — courses along the lateral pelvic wall into the obturator canal. It gives off pubic, anterior, and posterior branches. The posterior branch gives rise to the important 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 is dedicated to supplying the musculofascial structures of the pelvis and back. It includes the following vessels:
- Iliolumbar artery (a. iliolumbalis) — divides into lumbar and iliac branches, supplying the psoas major and iliacus muscles.
- Lateral sacral arteries (aa. sacrales laterales) — descend along the anterior surface of the sacrum, passing through the pelvic sacral foramina to supply spinal nerve roots and the 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 alongside the sciatic nerve. It gives off a companion artery to the sciatic nerve (a. comitans n. ischiadici) and supplies the posterior thigh muscles.
Important Anastomoses and Clinical Significance
The internal iliac artery system forms several critical vascular anastomoses, knowledge of which is essential for surgeons and traumatologists:
- Corona mortis (corona mortis): A clinically significant vascular connection between the pubic branch of the obturator artery and the pubic branch of the inferior epigastric artery. During pelvic fractures or surgical approaches to the groin, injury to this prominent anastomosis can result in massive, life-threatening hemorrhage.
- Crossing of the ureter and uterine artery: During gynecologic procedures (e.g., hysterectomy), the surgeon must account for the anatomical relationship where the ureter passes strictly inferior to the uterine artery, carrying a risk of accidental ligation.
- Gluteal anastomotic network: An extensive vascular network connecting the superior and inferior gluteal arteries with branches of the femoral circumflex arteries and the perforating branches of the deep femoral artery.
Briefly: answers to topical questions
What branches are given off by the internal pudendal artery in the ischioanal fossa and perineum?
Within the ischioanal fossa and perineum, the internal pudendal artery gives off several branches to the pelvic organs and external genitalia.
- Inferior rectal arteries (aa. rectales inferiores)
- Perineal artery (a. perinealis) — gives off posterior labial or scrotal branches.
- Artery of the bulb of the penis / vestibule (a. bulbi penis / a. bulbi vestibuli)
- Deep artery of the penis / clitoris (a. profunda penis/clitoridis)
- Dorsal artery of the penis / clitoris (a. dorsalis penis/clitoridis)
Additionally, the vessel gives off bulbar, urethral, and cavernosal branches.
With which arteries does the uterine artery anastomose?
The uterine artery forms anastomoses with vessels supplying the female reproductive organs.
- Ovarian artery (a. ovarica) — anastomoses with the ovarian branches of the uterine artery within the broad ligament of the uterus.
- Artery of the round ligament of the uterus (a. lig. teretis uteri) — connects with branches of the uterine artery ascending along the lateral margin of the uterus.
Which specific femoral arteries participate in the formation of the cruciate anastomotic network of the gluteal region alongside the gluteal arteries?
Branches of the deep femoral artery participate in forming the trochanteric/cruciate anastomosis of the gluteal region along with the superior and inferior gluteal arteries.
- Lateral femoral circumflex artery (a. circumflexa femoris lateralis) — contributes via its ascending branch (r. ascendens).
- Medial femoral circumflex artery (a. circumflexa femoris medialis) — contributes via its ascending branch.
- Perforating arteries (aa. perforantes) — specifically, the first perforating artery.
Which veins accompany the internal iliac artery, and what venous plexuses do they form?
The internal iliac artery is accompanied by the corresponding internal iliac vein (v. iliaca interna), which lies posterior to the artery. Its tributaries, accompanying the branches of the artery, form several venous plexuses:
- Superior gluteal veins (vv. gluteae superiores) — accompany the artery as paired trunks, forming a plexus around it.
- Lateral sacral veins (vv. sacrales laterales) — form the sacral venous plexus (plexus venosus sacralis) on the pelvic surface of the sacrum.
Which groups of lymph nodes are located along the course of the internal iliac artery and its branches?
The internal iliac lymph nodes (nodi lymphoidei iliaci interni) are located along the course of the internal iliac artery. They include the following groups:
- Superior and inferior gluteal nodes (nodi gluteales superiores et inferiores)
- Sacral nodes (nodi sacrales)
Visceral lymph nodes of the pelvis include:
- Paravesical nodes (nodi lymphoidei paravesicales)
- Parauterine nodes (nodi lymphoidei parauterini)
- Paravaginal nodes (nodi lymphoidei paravaginales)
- Pararectal / anorectal nodes
The English mnemonic "Water under the bridge" is exceptionally helpful for remembering the topography in the female pelvis: urine (water/ureter) always flows strictly under the artery (bridge/uterine artery).
Class and exam questions
How does the internal pudendal artery exit the pelvic cavity?
It leaves the pelvic cavity through the infrapiriform foramen (foramen infrapiriforme), curves around the ischial spine, and re-enters through the lesser sciatic foramen to reach the ischioanal fossa.
What is the characteristic feature of the umbilical artery in adults?
In adults, only its proximal part functions normally, giving off the superior vesical arteries. The distal segment of the vessel obliterates, transforming into the medial umbilical ligament.
What does the obturator artery supply?
It supplies the adductor muscles of the thigh, obturator muscles, and the skin of the medial aspect of the thigh. Importantly, it gives off the acetabular branch (r. acetabularis), which supplies the head of the femur, being of particular significance in childhood.
What else to study on this topic
- Topography and branches of the internal pudendal artery in Alcock's canal
- Mechanisms of formation of the gluteal arterial network
- Differences in the blood supply to male and female pelvic organs
- Variations in the origin of the obturator artery and the surgical significance of the "corona mortis"
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