The common iliac vein is one piece of a large system that allows blood circulation from the lower abdomen and legs. This vein is where the external iliac veins and internal iliac veins unite. As with all human veins, it follows along the path of its corresponding artery—in this case, the common iliac artery.
The common iliac vein is formed when the external iliac veins join the internal iliac veins. These veins are critical to the human circulatory system. They are responsible for draining blood from the legs and lower abdomen. This is an essential process that allows fresh blood to nourish the muscles and organs with vital nutrients and oxygen.
The common iliac vein is connected to a network of veins, also called plexuses, in the lower abdomen. There are two common iliac veins. Each vein begins at the brim of the pelvis and separately travels up each side of the pelvis to connect at the fifth lumbar vertebra.
External iliac veins are one of two veins that join to form the common iliac vein. They carry deoxygenated blood from the deep veins of the lower leg up into the lower region of the abdomen. These veins begin at the femoral vein, directly behind the inguinal ligament. The inferior epigastric vein drains used blood into the external iliac veins. They follow the external iliac arteries, which are responsible for carrying new blood to the lower abdomen and limbs.
The remaining veins that form the common iliac vein are the internal iliac veins. The internal iliac veins come from deep within the pelvic region and join the external iliac veins to form the common iliac vein. These veins drain deoxygenated blood from the organs of the reproductive, urinary, and digestive systems within the pelvic region. These organs include the rectum, bladder, and vagina or prostate, depending on gender. They also share a path with the internal iliac arteries, which supply fresh, oxygenated blood to these organs.
The common iliac vein meets its end where it combines with the opposite leg's common iliac vein at the fifth lumbar vertebra. At this juncture, the veins form the inferior vena cava. The inferior vena cava is the next step toward the heart. All the blood drained from the lower extremities will finally be filtered in the heart to be oxygenated. The fresh blood is then sent back down the arteries to continue the cycle.