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Structure

Spinal cord

Not medically reviewed · Content last updated · 2 min read ·

This is the date the draft was written, not a medical review date.

The spinal cord is the caudal continuation of the medulla oblongata within the vertebral canal. It conducts motor and sensory information between the brain and the body and mediates spinal reflexes.

Terminologia Anatomica (Latin): Medulla spinalis · Open in the 3D atlas

Location

From the foramen magnum to the conus medullaris, which ends at about L1-L2 in adults (variable; lower in children). Below it the lumbar cistern contains the cauda equina and filum terminale.

Structure

31 pairs of segments (8 cervical, 12 thoracic, 5 lumbar, 5 sacral, 1 coccygeal) with cervical and lumbar enlargements. Grey matter forms an H-shape (dorsal, lateral and ventral horns); white matter columns carry ascending (dorsal columns, spinothalamic, spinocerebellar) and descending (corticospinal, others) tracts. Cord segments lie higher than the corresponding vertebrae.

Blood supply

One anterior spinal artery (supplying the anterior two-thirds) and two posterior spinal arteries (posterior third), reinforced by segmental radicular arteries, notably the great radicular artery (of Adamkiewicz), usually arising on the left at about T9-L2. Venous drainage is to the internal vertebral venous plexus.

Innervation

Connections: each segment gives dorsal (sensory) and ventral (motor) roots that join to form a spinal nerve; descending tracts (corticospinal, reticulospinal, vestibulospinal, rubrospinal) act on the anterior horn motor neurons and autonomic cell columns (sympathetic T1-L2, parasympathetic S2-S4).

Function

It relays ascending sensory information (touch, proprioception, pain, temperature), carries descending voluntary and postural commands, contains reflex arcs, and gives origin to the somatic and autonomic outflow to the trunk and limbs.

Clinical correlations

Lesions produce level-dependent deficits: complete transection (spinal shock then spastic paralysis), Brown-Sequard syndrome (ipsilateral weakness and loss of proprioception, contralateral loss of pain and temperature), anterior cord syndrome and central cord syndrome. Cauda equina syndrome (saddle anaesthesia, sphincter dysfunction) is a surgical emergency; lumbar puncture is performed below the conus, typically at L3-L4 or L4-L5.

Common exam points

  • 31 segments; the adult conus medullaris ends at about L1-L2 (variable).
  • Cord segments lie above their vertebral levels; the cauda equina fills the lumbar cistern.
  • Anterior spinal artery supplies the anterior two-thirds; two posterior spinal arteries the dorsal columns.
  • Dorsal columns: fine touch and proprioception (ipsilateral); spinothalamic: pain and temperature (crosses at the cord level).
  • Brown-Sequard: ipsilateral motor and proprioceptive loss, contralateral pain and temperature loss.
  • Lumbar puncture below L2, usually L3-L4 or L4-L5.

References

  1. Drake RL, Vogl AW, Mitchell AWM. Gray's Anatomy for Students. Elsevier — Tier 3 (textbook)
  2. Moore KL, Dalley AF, Agur AMR. Clinically Oriented Anatomy. Wolters Kluwer, 8th edition (2018) — Tier 3 (textbook)
  3. Kandel ER, Koester JD, Mack SH, Siegelbaum SA. Principles of Neural Science. McGraw-Hill, 6th edition (2021) — Tier 3 (textbook)

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