Which Structure Is Highlighted Left Internal Iliac Artery

Navigating the intricate landscape of human anatomy can feel like embarking on an exploratory mission. The left internal iliac artery is one such critical anatomical structure, deeply embedded within the pelvis and playing a pivotal role in supplying blood to a myriad of vital organs and tissues. A thorough understanding of this artery, its branches, and the structures it serves, is paramount for medical professionals, students, and anyone keen on grasping the complexities of the human body.

Anatomy of the Left Internal Iliac Artery

The internal iliac artery, also known as the hypogastric artery, is a major vessel that originates as one of the two terminal branches of the common iliac artery. The common iliac arteries themselves arise from the abdominal aorta, the body's largest artery. The bifurcation, or splitting, of the common iliac arteries usually occurs around the level of the fourth lumbar vertebra (L4). From this point, each common iliac artery divides into the external and internal iliac arteries. The left internal iliac artery, therefore, is the branch on the left side of the body, responsible for supplying blood to the pelvic region.

The internal iliac artery is relatively short, typically measuring about 4 cm in length. It descends into the pelvis, medial to the external iliac artery and psoas major muscle. Near the superior border of the greater sciatic foramen, the internal iliac artery bifurcates into anterior and posterior divisions. These divisions give rise to a complex network of branches that perfuse various pelvic structures.

Branches of the Left Internal Iliac Artery

The branching pattern of the internal iliac artery is complex, exhibiting considerable individual variation. However, the general arrangement remains consistent. Understanding these branches is essential for comprehending the blood supply to the pelvic organs and the potential consequences of vascular compromise. The internal iliac artery branches into anterior and posterior divisions.

Anterior Division Branches:

1. Umbilical Artery:

   • In the fetus, the umbilical artery carries deoxygenated blood and waste products to the placenta. Postnatally, the proximal portion of the umbilical artery remains patent, giving rise to the superior vesical artery. The distal portion obliterates, becoming the medial umbilical ligament.
   • The superior vesical artery supplies the superior part of the bladder.

2. Obturator Artery:

   • The obturator artery courses along the lateral pelvic wall, exiting the pelvis through the obturator foramen alongside the obturator nerve and vein. It supplies the adductor muscles of the thigh, the iliacus muscle, and the hip joint.
   • In a small percentage of individuals, the obturator artery arises from the external iliac artery or the inferior epigastric artery as an aberrant obturator artery. This variation is clinically significant during surgical procedures like hernia repairs, where the aberrant artery is vulnerable to injury.

3. Inferior Vesical Artery:

   • This artery primarily supplies the base of the bladder, the prostate gland, and the seminal vesicles in males. It may also give rise to the artery to the vas deferens.
   • In females, the inferior vesical artery is often replaced by the vaginal artery.

4. Middle Rectal Artery:

   • The middle rectal artery supplies the rectum. It anastomoses (connects) with the superior rectal artery (a branch of the inferior mesenteric artery) and the inferior rectal artery (a branch of the internal pudendal artery), providing collateral circulation to the rectum.

5. Internal Pudendal Artery:

   • The internal pudendal artery is a major vessel supplying the perineum, the external genitalia, and the pelvic floor. It exits the pelvis through the greater sciatic foramen, curves around the ischial spine, and re-enters the pelvis through the lesser sciatic foramen.
   • Within the pudendal canal (Alcock's canal), it gives rise to several branches, including the inferior rectal artery, the perineal artery, the dorsal artery of the penis (or clitoris), and the artery of the bulb of the penis (or vestibule).

6. Inferior Gluteal Artery:

   • The inferior gluteal artery exits the pelvis through the greater sciatic foramen, inferior to the piriformis muscle. It supplies the gluteus maximus muscle, the hip joint, and the posterior thigh. It also contributes to the cruciate anastomosis around the hip joint.

7. Uterine Artery (in Females):

   • The uterine artery is a crucial vessel in females, supplying the uterus, the uterine tubes, and the vagina. It courses along the lateral aspect of the uterus, ascending towards the uterine horns.
   • Near the cervix, the uterine artery crosses over the ureter ("water under the bridge"), a clinically important relationship during hysterectomies.
   • The uterine artery anastomoses with the ovarian artery, providing collateral circulation to the female reproductive organs.

8. Vaginal Artery (in Females):

   • The vaginal artery supplies the vagina. It often arises from the uterine artery or directly from the internal iliac artery. It may replace the inferior vesical artery in females.

Posterior Division Branches:

1. Iliolumbar Artery:

   • The iliolumbar artery ascends superiorly, passing behind the obturator nerve and the external iliac vessels. It divides into lumbar and iliac branches.
   • The lumbar branch supplies the psoas major and quadratus lumborum muscles, sending a spinal branch to the vertebral canal to supply the spinal cord and meninges. The iliac branch supplies the iliacus muscle and the ilium.

2. Lateral Sacral Arteries:

   • These arteries supply the sacrum, the erector spinae muscles, and the skin over the sacrum. They enter the sacral foramina to supply the spinal cord and meninges.

3. Superior Gluteal Artery:

   • The superior gluteal artery is the largest branch of the internal iliac artery and exits the pelvis through the greater sciatic foramen, superior to the piriformis muscle.
   • It supplies the gluteus medius, gluteus minimus, and tensor fasciae latae muscles. It also contributes to the blood supply of the hip joint. Injury to the superior gluteal artery can lead to Trendelenburg gait due to weakness of the gluteus medius muscle.

Structures Highlighted by the Left Internal Iliac Artery

The left internal iliac artery and its branches supply a wide array of vital structures within the pelvis and perineum. Here’s a detailed breakdown of the key areas and organs that benefit from this arterial network:

1. Pelvic Organs:

   • Bladder: The superior and inferior vesical arteries provide blood to the bladder, ensuring its proper function in urine storage and expulsion.
   • Rectum: The middle rectal artery, along with the superior and inferior rectal arteries, supplies the rectum, crucial for waste storage and elimination.
   • Uterus: (In females) The uterine artery is the primary blood supply to the uterus, essential for menstruation, pregnancy, and childbirth.
   • Vagina: (In females) The vaginal artery supplies the vagina, supporting its role in sexual function and childbirth.
   • Prostate Gland and Seminal Vesicles: (In males) The inferior vesical artery supplies these structures, which are vital for male reproductive function.

2. Pelvic Musculature:

   • Obturator Muscles: The obturator artery supplies the obturator internus and externus muscles, crucial for hip rotation.
   • Gluteal Muscles: The superior and inferior gluteal arteries supply the gluteus maximus, medius, and minimus muscles, essential for hip extension, abduction, and stability.
   • Iliacus and Psoas Muscles: The iliolumbar artery contributes to the blood supply of these muscles, which are important for hip flexion and spinal stability.

3. Perineum and External Genitalia:

   • Perineal Structures: The internal pudendal artery supplies the perineum, including the muscles of the pelvic floor, which are essential for urinary and fecal continence, as well as sexual function.
   • External Genitalia: The internal pudendal artery supplies the penis (or clitoris), scrotum (or labia), and associated structures, supporting sexual function and sensation.

4. Hip Joint and Thigh:

   • Hip Joint: Branches from the obturator, superior gluteal, and inferior gluteal arteries contribute to the blood supply of the hip joint, ensuring its proper function and preventing avascular necrosis of the femoral head.
   • Thigh Muscles: The obturator and inferior gluteal arteries supply the adductor muscles and posterior thigh muscles, supporting hip adduction and knee flexion.

5. Sacrum and Lower Spine:

   • Sacrum: The lateral sacral arteries supply the sacrum, providing nutrients and oxygen to the bone and surrounding tissues.
   • Spinal Cord and Meninges: Spinal branches from the iliolumbar and lateral sacral arteries supply the spinal cord and meninges within the vertebral canal, ensuring proper neurological function.

Clinical Significance

Understanding the anatomy and function of the left internal iliac artery is crucial for various clinical scenarios. Here are some notable examples:

1. Pelvic Surgery:

   • During pelvic surgeries, such as hysterectomies, prostatectomies, and colorectal resections, surgeons must have a thorough understanding of the internal iliac artery and its branches to avoid inadvertent injury.
   • Ligation (tying off) of the internal iliac artery may be necessary to control severe pelvic hemorrhage, such as in cases of postpartum hemorrhage or trauma. Knowing the branching pattern helps surgeons selectively ligate the appropriate vessels while preserving blood flow to vital organs.

2. Vascular Disease:

   • Atherosclerosis (plaque buildup) can affect the internal iliac artery, leading to pelvic ischemia (reduced blood flow). This can manifest as buttock claudication (pain with walking), erectile dysfunction (in males), or pelvic pain.
   • Aneurysms (bulges) can develop in the internal iliac artery, posing a risk of rupture and life-threatening hemorrhage. Early diagnosis and treatment are essential.

3. Trauma:

   • Pelvic fractures can injure the internal iliac artery and its branches, leading to significant bleeding. Prompt diagnosis and intervention, such as angiographic embolization (blocking the bleeding vessel), are crucial to control hemorrhage and stabilize the patient.

4. Urological Procedures:

   • During procedures involving the bladder, prostate, or ureters, knowledge of the internal iliac artery and its branches is essential to avoid vascular injury and ensure adequate blood supply to the affected organs.

5. Gynecological Procedures:

   • In gynecological surgeries, such as hysterectomies and oophorectomies, the uterine artery (a branch of the internal iliac artery) is carefully identified and ligated to prevent bleeding.
   • Understanding the relationship between the uterine artery and the ureter is crucial to avoid ureteral injury during these procedures.

6. Interventional Radiology:

   • Interventional radiologists use angiographic techniques to diagnose and treat various conditions affecting the internal iliac artery and its branches.
   • Embolization can be used to control pelvic hemorrhage, treat aneurysms, or devascularize tumors. Stenting can be used to treat stenoses (narrowing) of the internal iliac artery.

Variations

The branching pattern of the left internal iliac artery can vary considerably among individuals. Some common variations include:

• Origin of the Obturator Artery: In some cases, the obturator artery may arise from the external iliac artery or the inferior epigastric artery instead of the internal iliac artery.
• Origin of the Uterine Artery: The uterine artery may arise directly from the internal iliac artery or as a branch of another vessel, such as the vaginal artery.
• Number and Size of Branches: The number and size of the branches of the internal iliac artery can vary, with some branches being absent or duplicated.

These variations are important to be aware of during surgical procedures to avoid inadvertent injury to the vessels.

Imaging

Various imaging modalities can be used to visualize the left internal iliac artery and its branches:

• Computed Tomography Angiography (CTA): CTA is a non-invasive imaging technique that uses X-rays and contrast dye to create detailed images of the blood vessels. It is commonly used to evaluate aneurysms, stenoses, and other vascular abnormalities.
• Magnetic Resonance Angiography (MRA): MRA is another non-invasive imaging technique that uses magnetic fields and radio waves to create images of the blood vessels. It is particularly useful for visualizing the internal iliac artery and its branches without using ionizing radiation.
• Conventional Angiography: Conventional angiography is an invasive imaging technique that involves inserting a catheter into an artery and injecting contrast dye to visualize the blood vessels. It is often used to guide interventional procedures, such as embolization and stenting.
• Ultrasound: Ultrasound can be used to visualize the internal iliac artery and its branches, particularly in pregnant women. Doppler ultrasound can be used to assess blood flow in the vessels.

Development

The development of the internal iliac artery is complex and involves the remodeling of embryonic vessels. The internal iliac artery arises from the umbilical artery, which carries deoxygenated blood from the fetus to the placenta. After birth, the umbilical artery obliterates, but its proximal portion persists as the superior vesical artery. The other branches of the internal iliac artery develop from the primitive internal iliac artery.

Conclusion

The left internal iliac artery is a critical vessel that supplies blood to a wide range of vital structures within the pelvis and perineum. A thorough understanding of its anatomy, branching pattern, clinical significance, and variations is essential for medical professionals involved in pelvic surgery, vascular disease management, trauma care, urological procedures, gynecological procedures, and interventional radiology. By mastering the intricacies of this arterial network, healthcare providers can optimize patient outcomes and ensure the delivery of high-quality care.