The Lumbar Plexus

Video Description

Lumbar plexus

The lumbar plexus is a complex neural network formed by the lower thoracic and lumbar ventral nerve roots (T12 to L5) which supplies motor and sensory innervation to the lower limb and pelvic girdle.

origin: ventral rami of T12 to L5

course: formed within the substance of the psoas major muscle, anterior to the lumbar transverse processes

major (terminal) branches
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?Iliohypogastric nerve
ilioinguinal nerve
genitofemoral nerve
lateral femoral cutaneous nerve
femoral nerve
obturator nerve

motor supply: lower limb and pelvic girdle

sensory supply: lower anterior abdominal wall, groin, upper thigh and pudenda

Gross anatomy
The branches that arise from the lumbar plexus are:

subcostal nerve: T12
Iliohypogastric nerve: L1
ilioinguinal nerve: L1
genitofemoral nerve: L1, 2
lateral femoral cutaneous nerve: L2, 3
femoral nerve: L2, 3, 4
obturator nerve: L2, 3, 4
lumbosacral trunk: L4, 5
this contributes to the sacral plexus
The branches of the lumber plexus are covered in this mnemonic.

Variant anatomy

Variation in the lumbar plexus appears to be common (~90% in one study) 1:

absent iliohypogastric nerve (~20%)
early branching (within psoas muscle) of the genitofemoral nerve (~20%)
accessory obturator nerve (~10%)