External Iliac Arteries

1. Overview

The external iliac arteries are major blood vessels that supply oxygenated blood to the lower limbs, including the legs and pelvis. They are a continuation of the common iliac arteries and are responsible for carrying blood from the aorta to the femoral artery, which further branches into smaller arteries in the leg. The external iliac arteries are critical for maintaining blood flow to the lower body and play a vital role in supporting the musculature and tissues of the lower extremities. The arteries also provide blood to the abdominal wall and organs near the pelvis. Understanding the anatomy and function of the external iliac arteries is important for diagnosing and treating vascular diseases, including peripheral artery disease (PAD) and aneurysms.

2. Location

The external iliac arteries are located in the pelvic cavity, on either side of the body. They originate from the bifurcation of the common iliac arteries, which occurs at the level of the fourth lumbar vertebra (L4). After the bifurcation, each external iliac artery travels laterally and downwards towards the lower extremities. The external iliac artery passes beneath the inguinal ligament and enters the thigh, where it continues as the femoral artery. This artery is situated alongside the internal iliac artery, which supplies the pelvic organs, and the two arteries run parallel to the pelvis, separated by the psoas major muscle.

3. Structure

The external iliac arteries are large, muscular arteries that have structural features designed to handle high-pressure blood flow. Key structural characteristics of the external iliac arteries include:

• Origin: The external iliac arteries originate from the common iliac arteries, which bifurcate from the abdominal aorta. This bifurcation typically occurs at the level of the L4 vertebra.

• Course: The external iliac arteries travel down the pelvis, passing beneath the inguinal ligament, and then continue as the femoral arteries in the thigh.

• Size and Diameter: The external iliac arteries have a relatively large diameter, typically around 7 to 10 millimeters, although this can vary based on individual anatomy and health conditions.

• Wall Composition: Like all arteries, the external iliac arteries consist of three layers:

  • Intima: The innermost layer composed of endothelial cells that provide a smooth surface for blood flow.

  • Media: The middle layer composed of smooth muscle cells and elastic fibers, allowing the artery to expand and contract with each heartbeat.

  • Adventitia: The outer layer made of connective tissue that provides structural support and anchors the artery to surrounding tissues.

• Branches: The external iliac arteries give rise to several smaller branches that supply blood to the abdominal wall and the lower limbs:

  • Inferior epigastric artery: Supplies the lower part of the abdominal wall and the rectus abdominis muscle.

  • Deep circumflex iliac artery: Supplies the iliac region and the muscles of the lower abdominal wall.

4. Function

The primary function of the external iliac arteries is to supply oxygenated blood to the lower extremities and pelvic region. Some of the key functions of the external iliac arteries include:

• Blood supply to the lower limbs: The external iliac arteries provide the majority of the blood supply to the legs. Once they pass beneath the inguinal ligament, they become the femoral arteries, which continue down the legs to supply blood to the thigh, knee, and lower legs.

• Blood supply to the abdominal wall: The external iliac arteries supply blood to the lower part of the abdominal wall via the inferior epigastric artery and the deep circumflex iliac artery.

• Supplying pelvic structures: Although the internal iliac artery is the main artery that supplies blood to the pelvic organs, the external iliac arteries also provide some blood supply to structures in the lower pelvis and groin area.

5. Physiological Role(s)

The external iliac arteries play several key physiological roles that are essential for the proper function of the lower body. These roles include:

• Oxygen and nutrient delivery to the lower limbs: By supplying the femoral artery and its branches, the external iliac arteries ensure that the muscles, skin, and bones of the legs receive a continuous supply of oxygenated blood. This is critical for maintaining muscle function, particularly during physical activity like walking, running, or standing.

• Support of movement and physical activity: The external iliac arteries support the movement of the lower extremities by providing blood to the muscles of the thighs, knees, and lower legs. These muscles require a constant supply of oxygen and nutrients to contract and facilitate movement.

• Facilitating circulatory homeostasis: By supplying blood to the lower body, the external iliac arteries help maintain circulatory homeostasis, ensuring that the lower limbs are well-perfused and the veins return blood back to the heart efficiently.

• Support during exertion: During exercise or physical exertion, the demand for oxygen and nutrients in the muscles of the legs increases. The external iliac arteries help meet this demand by ensuring that sufficient blood flow is delivered to the lower extremities, enabling optimal performance and reducing the risk of fatigue.

6. Clinical Significance

The external iliac arteries are clinically significant due to their role in supplying blood to the lower limbs and pelvic region. Various conditions can affect these arteries, leading to serious cardiovascular and mobility issues. Some of the key clinical conditions associated with the external iliac arteries include:

• Peripheral artery disease (PAD): PAD occurs when there is a narrowing or blockage of the arteries in the legs, including the external iliac arteries. This can lead to pain, cramping, numbness, and difficulty walking. In severe cases, PAD can lead to non-healing ulcers and tissue death. Treatment options include lifestyle changes, medications, angioplasty, or surgery to restore blood flow.

• Atherosclerosis: Atherosclerosis, or the buildup of fatty deposits in the arteries, can affect the external iliac arteries, leading to reduced blood flow to the legs and pelvis. This condition can contribute to PAD and increase the risk of heart attack or stroke. Treatment may involve medications such as statins, blood pressure management, and surgical procedures like bypass surgery or stenting.

• External iliac artery aneurysm: An aneurysm in the external iliac artery occurs when the artery becomes abnormally dilated due to a weakened wall. If left untreated, the aneurysm can rupture, leading to life-threatening internal bleeding. Surgical intervention is often required to repair the aneurysm.

• External iliac artery dissection: Dissection of the external iliac artery occurs when there is a tear in the inner layer of the artery wall. This can lead to reduced blood flow to the lower limbs and abdominal organs, and in some cases, can cause acute pain or stroke. Treatment typically involves blood thinners or surgery to repair the artery.

• Venous insufficiency: Though primarily a venous condition, venous insufficiency in the legs can be exacerbated by arterial diseases such as atherosclerosis or PAD in the external iliac arteries. This can lead to swelling, varicose veins, and ulcers. Managing the underlying arterial condition is crucial for improving venous return.

The external iliac arteries are essential for supplying blood to the lower extremities and pelvis. Dysfunction or blockage of these arteries can lead to serious health problems, including pain, ulcers, or even loss of limb function. Early diagnosis, treatment, and preventive measures are crucial for maintaining the health of these arteries and ensuring proper blood flow to the lower body.