The median sacral artery or arteria sacralis mediana in Latin is a small unpaired parietal branch that arises from the posterior surface of the abdominal aorta, just above the level of its bifurcation at the fourth lumbar vertebra L4. It is one of the three posterior branches of the abdominal aorta, the other two being: the inferior phrenic arteries, and the lumbar arteries. These vessels are responsible for the blood supply of the diaphragm or body wall. Although markedly smaller, the median sacral artery is considered the midline “continuation” of the aorta.
It descends over the anterior surface of the lower fourth and fifth lumbar vertebrae (L4, L5), and then over the anterior surface of both the sacrum and coccyx as well. The left common iliac vein crosses the median sacral artery at the level of the fifth lumbar vertebra (L5). It often gives off a small lumbar artery, the arteria lumbalis ima, whom small branches reach the anorectum (the posterior part of the rectum) via the anococcygeal ligament, where it anastomoses with the superior and middle rectal arteries. Anterior to the fifth lumbar vertebra (L5), the median sacral artery anastomoses with the iliolumbar artery through a lumbar branch. On the other hand, anterior to the sacrum, it anastomoses with the lateral sacral arteries, where it then proceeds to send off branches to the anterior sacral foramina.
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