The medial arcuate ligament (also medial lumbocostal arch) is a tendinous fascia that arches over the psoas major muscle as it passes through the diaphragm.

Structure

The medial arcuate ligament is an arch in the fascia covering the upper part of the psoas major. It is attached to the side of the body of the first or second lumbar vertebra; laterally, it is fixed to the front of the transverse process of the first and, sometimes also, to that of the second lumbar vertebra.

It lies between the lateral arcuate ligament

Lateral arcuate ligament

The lateral arcuate ligament is a ligament under the diaphragm that arches across the upper part of the quadratus lumborum...

 and the midline median arcuate ligament

Median arcuate ligament

The median arcuate ligament is a ligament under the diaphragm that connects the right and left crura of diaphragm.-Structure:The median arcuate ligament is formed by the right and left crura of the diaphragm...

.

The sympathetic chain enters the abdomen by passing deep to this ligament.

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