Muscle · Lumbar spine

Intertransversarii laterales lumborum

Musculi intertransversarii laterales lumborum

Small muscles running vertically between the transverse processes of adjacent lumbar vertebrae, on the outer side of the pair — the medial slips sit closer to the midline behind them. Each crosses one segment and bends it toward its own side, with a lever so short that the movement is nominal; like the other tiny paraspinal muscles they are read as segmental controllers. What genuinely separates them from their medial partners is their nerve: the lateral set is supplied by the VENTRAL rami of the lumbar spinal nerves, while almost everything else at this depth in the back takes the dorsal rami. That split is a real developmental boundary, not a bookkeeping detail.