L1 — first lumbar vertebra (Vertebra lumbalis prima)
Educational content only — not medical advice.
Anatomy
L1, the first of five massive lumbar vertebrae carrying the trunk's weight: a broad kidney-shaped body, a hatchet-shaped horizontal spinous process and slender transverse processes. Below it the spinal cord ends as the conus medullaris, normally at L1–L2 — lumbar puncture is performed beneath, never at this level.
Clinical notes
Lumbar disc herniation at L1 may compress the L2 root, producing anterior-thigh and groin pain (femoral distribution) rather than the below-knee sciatica of the lower levels.
Related structures
Educational references
FAQ
What is the role of the L1 — first lumbar vertebra?
L1, the first of five massive lumbar vertebrae carrying the trunk's weight: a broad kidney-shaped body, a hatchet-shaped horizontal spinous process and slender transverse processes. Below it the spinal cord ends as the conus medullaris, normally at L1–L2 — lumbar puncture is performed beneath, never at this level.
Why is the L1 — first lumbar vertebra clinically important?
Lumbar disc herniation at L1 may compress the L2 root, producing anterior-thigh and groin pain (femoral distribution) rather than the below-knee sciatica of the lower levels.
Source & license
Derived from Z-Anatomy (Gauthier Kervyn et al.), CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0/); upstream geometry from BodyParts3D, © The Database Center for Life Science. license details