Final answer:
The external iliac artery is not a direct branch of the abdominal aorta; it originates from the division of the common iliac arteries, which itself is a bifurcation of the abdominal aorta at the level of the L4 vertebra.
Step-by-step explanation:
The abdominal aorta is a major artery that extends from the thoracic aorta through the aortic hiatus in the diaphragm and down to around the level of the fourth lumbar vertebra (L4), where it bifurcates into the common iliac arteries. Several important single branches emerge from the abdominal aorta, including the celiac trunk (or celiac artery), the superior mesenteric artery (SMA), and the inferior mesenteric artery (IMA). Other significant paired arteries include the inferior phrenic arteries, adrenal arteries, renal arteries, gonadal arteries, and lumbar arteries. However, the external iliac artery is not a direct branch of the abdominal aorta, as it comes from the division of the common iliac arteries.