L4 spinal nerve

Nervus spinalis L4

NervousNervesAbdomenLeft and right

View left in 3D View right in 3D

What it is
The L4 spinal nerve leaves the spinal canal between L4 and L5. Its sensory (dorsal) and motor (ventral) roots meet just beyond the dorsal root ganglion; the short mixed nerve then splits into a small dorsal ramus for the back muscles and skin and a larger ventral ramus, which splits between the lumbar plexus and the lumbosacral trunk.
Function
Carries motor fibres to the muscles of its segment (myotome) and sensation back from its strip of skin (dermatome): the medial leg and the medial ankle.
Size
About 4-5 mm thick; the mixed nerve is only ~1 cm long before it divides
Clinical note
Test: the knee-jerk reflex and ankle dorsiflexion; compressed by an L3/4 disc or foraminal narrowing.

Nearby nervous structures 10th intercostal nerve, 11th intercostal nerve, Celiac plexus and ganglia, Enteric (myenteric) plexus - marker, L1 spinal nerve, L2 spinal nerve, L3 spinal nerve, L4 dorsal root ganglion, L5 spinal nerve, Superior mesenteric plexus