Quick Facts
Origin: In or just lateral to the intervertebral foramen below the fifth lumbar (L5) vertebra.
Course: Medially through the intervertebral foramen and superiorly towards the posterior surface of the appropriate spinal cord level.
Branches: Unnamed rootlets just prior to entering the spinal cord.
Supply: Sensory innervation from the skin of the lower back, lateral leg, and dorsal and plantar surfaces of the foot.
Origin
The posterior root of the fifth lumbar nerve originates, in or just lateral, to the intervertebral foramen, inferior to the fifth lumbar (L5) vertebra and superior to the sacrum. It is at this point that the fifth lumbar nerve splits into anterior and posterior roots.
Course
The posterior root of the fifth lumbar nerve runs medially through the intervertebral foramen. Inside the vertebral canal, it runs superiorly towards its corresponding spinal cord level. The posterior root runs posterior to the denticulate ligament and splits into smaller rootlets, before entering the dorsal aspect of the spinal cord.
Branches
The posterior root of the fifth lumbar nerve branches into several smaller rootlets before entering the dorsal aspect of the spinal cord.
Supplied Structures
The posterior root of the fifth lumbar nerve carries sensory information from the skin of the lower back, lateral leg, and dorsal and plantar surfaces of the foot. Innervation of the foot is primarily of the medial surfaces.
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