Friday, December 2, 2011
The lumbosacral plexus is formed by the anterior branches of the lumbar and sacral spinal nerves. Its branches provide sensory and motor innervation to the lower limb. The branches of lumbar spinal nerves L1–L3 and part of L4 form the lumbar plexus, the roots of which lie within the psoas muscle. The obturator nerve and the femoral nerve originate from here, in addition to several short muscular branches. The remainder of the fourth lumbar nerve and the L5 nerve join to form the lumbosacral trunk, which then unites in the small pelvis with sacral branches 1 – 3 to form the sacral plexus. The sacral branches emerge from the anterior sacral foramina of the sacrum and form together with the lumbosacral trunk the sacral plexus; the main nerves originating from here are the sciatic nerve (common peroneal nerve and tibial nerve).