"The lumbosacral plexus are a network of nerves arising from the ventral rami of L1–L5, S1-S4 nerve roots. The nerves of lumbar plexus emerge from within the psoas major muscle and they are described in relation to this muscle. There are certain nerves that arise only from the lumbar plexus, others only from the sacral plexus, and some receive a contribution from both. The lumbosacral trunk (L4 and L5) joins the network of the sacral ventral rami (S1–S4) to form the lumbosacral plexus.
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