Spine & embryology · Interactive 3D

Lumbar spine & cauda equina

The lumbar spine and sacrum from behind with the laminae removed, showing the conus medullaris, the cauda equina in the canal, the intervertebral discs and the nerve roots leaving below each pedicle.

Interactive — drag to rotate

Lumbar spine & cauda equina — still render

AI-assisted model. Labels checked against standard anatomy references; specialist review pending.

What to look at

1The cord ends at the conus medullaris at about L1–L2 in adults; below that the canal holds the cauda equina.
2Each lumbar root leaves the canal below the pedicle of its own vertebra: the L4 root exits at the L4–L5 foramen.
3A posterolateral disc prolapse at L4–L5 compresses the traversing L5 root; a far-lateral prolapse at the same level compresses the exiting L4 root.
4Compression of the whole cauda equina causes saddle anaesthesia and bladder, bowel and sexual dysfunction — a surgical emergency.

Hotspots

1Conus medullaris — The end of the spinal cord at about L1–L2.
2Cauda equina — Lumbar and sacral roots descending in the dural sac.
3L3 nerve root exiting below the L3 pedicle — Each lumbar root exits below the pedicle of the same-numbered vertebra.
4L4–L5 disc — With L5–S1, the commonest level for disc prolapse.
5L3 transverse process — The longest of the lumbar transverse processes.
6Sacrum — Five fused vertebrae; S2–S4 roots supply the bladder and anal sphincter.

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