Spinal Cord Anatomy: Extent, Structure & Function

The adult spinal cord does not extend to the coccyx. It terminates at the level of the first or second lumbar vertebra (L1–L2) in most adults, forming the conus medullaris. Below this, the cauda equina—a bundle of nerve roots—continues within the vertebral canal to the sacral and coccygeal levels.

Key Anatomical Points

• Origin: Continuous with the medulla oblongata at the foramen magnum.
• Termination: Conus medullaris at L1–L2 (varies slightly).
• Cauda equina: Lumbar, sacral, and coccygeal nerve roots descending from the conus.
• Protection: Encased in the vertebral column, surrounded by meninges and cerebrospinal fluid.
• Function: Major conduit for motor and sensory signals between brain and body; houses reflex arcs.

Clinical Relevance

Lumbar punctures are performed below L2 (typically L3–L4 or L4–L5) to avoid spinal cord injury. Spinal anesthesia also targets the subarachnoid space below the cord's end.