The iliac artery system is a major pathway within the body’s arterial network, delivering oxygenated blood to the entire lower half of the torso and the lower limbs. These paired, high-pressure vessels channel blood flow from the main trunk of the aorta, distributing it into the vascular beds of the pelvis and legs. This system ensures that structures vital for movement, waste processing, and reproduction receive necessary nutrients and oxygen. Understanding the iliac arteries involves tracing their origin from the aorta and following their division into specialized branches.
Anatomical Position and Origin
The common iliac arteries begin in the lower abdomen, marking the termination of the abdominal aorta. This division, known as the aortic bifurcation, typically occurs at the level of the fourth lumbar vertebra (L4). The right and left common iliac arteries run downward and laterally, traveling along the medial border of the psoas major muscles. These large vessels are approximately 4 centimeters long in adults.
Each common iliac artery descends until it reaches the pelvic brim and the sacroiliac joint. At this point, each vessel splits into two main vessels: the External Iliac Artery and the Internal Iliac Artery. This bifurcation defines the entry point for blood flow into the deep pelvic structures and the legs. Common iliac arteries are accompanied by the common iliac veins, which lie posteriorly, carrying deoxygenated blood back toward the heart.
The Major Branches and Their Destinations
The common iliac artery’s split creates two functionally distinct vessels that supply the lower body. The External Iliac Artery is the larger branch, primarily serving as the main blood supply for the lower limb. This vessel continues inferiorly, passing deep to the inguinal ligament in the groin area. Once it crosses this ligament, the External Iliac Artery is renamed the Femoral Artery, which supplies the thigh, knee, and foot.
The External Iliac Artery provides two branches before becoming the femoral artery: the inferior epigastric artery and the deep circumflex iliac artery. These vessels supply the muscles of the lower abdominal wall, including the rectus abdominis and the oblique muscles. The second major division, the Internal Iliac Artery, is shorter and supplies the entire pelvic cavity. It descends into the pelvis, branching extensively to supply the viscera and walls of this region.
Internal Iliac Artery Branches
The complex branching pattern of the Internal Iliac Artery ensures blood reaches the urinary bladder, the rectum, and reproductive organs (such as the uterus and prostate). Its branches, including the gluteal arteries, also exit the pelvis to supply the muscles of the buttock and the medial part of the thigh. This network, often called the hypogastric artery, consistently provides for the deep pelvic structures.
The Functional Role in Circulation
The function of the iliac arteries is to act as a distribution hub for systemic circulation below the waist. They deliver a significant volume of oxygenated blood under high pressure to the entire lower half of the body. This robust flow meets the metabolic demands of the large muscle groups in the legs, which require substantial blood supply for movement.
The system also maintains consistent perfusion to the internal organs housed within the pelvic cavity, including the bladder, intestines, and reproductive organs. By distributing flow from the abdominal aorta into two high-capacity pathways, the iliac arteries ensure oxygen and nutrients reach these distant tissues efficiently. The internal iliac artery also provides collateral circulation, a network of smaller vessels that can partially sustain blood flow if a main artery is narrowed or blocked.
Clinical Significance and Procedures
The iliac arteries are medically important due to their susceptibility to vascular disease and their utility as access points for procedures. Atherosclerosis, characterized by plaque buildup, is the most common pathology, leading to narrowing (stenosis) or complete blockage (occlusion). This condition is a primary cause of Peripheral Artery Disease (PAD) in the lower limbs, manifesting as pain during walking (intermittent claudication) or critical limb ischemia.
The arteries can also develop aneurysms, which are weakened, bulging spots in the vessel wall that carry a risk of rupture. Clinicians frequently use the iliac arteries, accessed via the femoral artery in the groin, as a gateway to the central circulation. This access allows for angiography, which uses dye and X-rays to visualize blood flow, or for therapeutic interventions like angioplasty and stenting. Stenting involves deploying a wire mesh tube to hold open a narrowed iliac artery, restoring blood flow to the legs and pelvis.