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Other Terms: Colon descendens, Côlon descendant
The descending colon descends almost vertically through the left lumbar region into the left iliac fossa. At the lateral border of the psoas muscle, it terminates in the sigmoid colon. At its commencement, it is attached to the diaphragm, opposite the tenth and eleventh ribs, by a fold of peritoneum, the phrenicoligament, upon which rests the lower end of the spleen. Like the ascending colon, it is fixed to the posterior wall of the abdomen by extraperitoneal connective tissue and the peritoneum which covers it in front and on the sides. A mesocolon with its two layers in contact is found more frequently on this side than on the right side, being present in about thirty-five percent of cases. The descending colon is smaller than the ascending, more deeply situated, and more movable. Behind the descending colon are the left crus of the diaphragm, the left kidney, and the quadratus lumborum muscle. To its medial side and in front are the convolutions of the small intestine. On its lateral side is the abdominal wall.