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Robotic Spine Universe

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The spinal cord

The part of the central nervous system inside the vertebral column. How it is built from grey horns and white columns, why it is shorter than the column, and how its regions are named.

Updated 2026-10-024 sources

Depth:

Why it matters

Every signal between the brain and the body below the head passes through the spinal cord: the major ascending and descending pathways between the cord and the brain pass through the brainstem [1]. The cord also does work of its own: the coordination of reflexes depends on sensory and motor pathways meeting inside it [1].

What it is

The central nervous system is the brain and the spinal cord; everything else is the peripheral nervous system [2]. The spinal cord is contained within the vertebral cavity of the vertebral column [2].

  • Its surface is marked in front by the anterior median fissure and behind by the posterior median sulcus [1].
  • In cross-section, grey matter in the middle forms horns, and white matter around it forms columns [1].
  • Its regions are named for the level at which their spinal nerves pass through the intervertebral foramina [1].

What it does

Ascending tracts in the white columns carry sensory information up to the brain, and descending tracts carry motor commands down from it [1]. The posterior columns are made of ascending tracts; the anterior and lateral columns hold both ascending and descending tracts [1].

The grey matter processes and sends: the posterior horn is responsible for sensory processing and the anterior horn sends motor signals to the skeletal muscles [1].

How it works

The cord is organised from front to back. During development it is divided into the basal plate, near the ventral midline, which gives rise to motor neurons, and the alar plate on the dorsal side, which gives rise to neurons that receive sensory input [1].

The cervical and lumbar parts of the cord have enlargements, which come from larger populations of neurons [1]. The lateral horn, found only in the thoracic, upper lumbar and sacral regions, holds the cell bodies of autonomic motor neurons [1].

Why it is built this way

The cord keeps the tube shape of its embryonic origin: while the brain develops from expansions of the neural tube into vesicles, the spinal cord keeps the tube structure and is only specialised into regions [1]. It develops from the posterior part of the neural tube [3].

It is shorter than the column because it does not grow significantly longer after the first or second year, while the skeleton keeps growing [1]. The lower nerves grow with the column and form the cauda equina [1].

Normal behaviour

Where the cord ends differs between people. In MRI of 629 healthy adults the most common level was L1, and pelvic incidence and height were significant factors in the level [4].

When it does not behave

If the neural tube fails to close where the spinal cord forms, the result is spina bifida [3]. In the mildest type, spina bifida occulta, the vertebral bones do not fully surround the cord but the cord itself is not affected [3].

Common misconceptions

Misconception: The spinal cord runs the whole length of the back.

It stops well above the end of the column, because it stops lengthening after the first year or two while the skeleton keeps growing [1, 4].

Check yourself

Which part of the grey matter sends motor signals to the skeletal muscles?

The anterior horn [1].

What do the posterior columns of white matter carry?

Ascending tracts, carrying sensory information up to the brain [1].

Read next

References

  1. Betts JG, Young KA, Wise JA, Johnson E, Poe B, Kruse DH, et al.. 13.2 The Central Nervous System. Anatomy and Physiology 2e. OpenStax. 2022. https://openstax.org/books/anatomy-and-physiology-2e/pages/13-2-the-central-nervous-system
  2. Betts JG, Young KA, Wise JA, Johnson E, Poe B, Kruse DH, et al.. 12.1 Basic Structure and Function of the Nervous System. Anatomy and Physiology 2e. OpenStax. 2022. https://openstax.org/books/anatomy-and-physiology-2e/pages/12-1-basic-structure-and-function-of-the-nervous-system
  3. Betts JG, Young KA, Wise JA, Johnson E, Poe B, Kruse DH, et al.. 13.1 The Embryologic Perspective. Anatomy and Physiology 2e. OpenStax. 2022. https://openstax.org/books/anatomy-and-physiology-2e/pages/13-1-the-embryologic-perspective
  4. Nakashima H, Ito K, Katayama Y, Tsushima M, Ando K, Kobayashi K, et al.. The Level of Conus Medullaris in 629 Healthy Japanese Individuals. Journal of Clinical Medicine. 2021;10(14):3182. doi:10.3390/jcm10143182

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