Lumbosacral trunk

The lumbosacral trunk is a cord-like structure that arises from the ventral rami of the fourth lumbar nerve (part of L4) and the fifth lumbar nerve (entire L5). This trunk serves as a connection between the lumbar plexus (Read more!) and the sacral plexus (Read more!). It is positioned anterior to the transverse processes of the lumbar vertebrae on the medial side of the psoas major muscle (also posterior to it).