The spinal cord is a long, thin, tubular structure made up of nervous tissue that extends from the brainstem down through the spinal column. It acts as the main pathway for transmitting information between the brain and the rest of the body. The colour of the spinal cord can provide insights into its anatomy and function. In this article, we will examine the external colour of the healthy human spinal cord.
Anatomy of the Spinal Cord
The spinal cord is protected by the bony vertebral column and several membranes called meninges. From the outside in, the meningeal layers surrounding the spinal cord are:
- Dura mater – Tough, outermost layer
- Arachnoid mater – Web-like middle layer
- Pia mater – Delicate, innermost layer adhering to surface of spinal cord
The subarachnoid space between the arachnoid and pia contains cerebrospinal fluid which helps cushion the spinal cord.
Gross External Anatomy
In a healthy spinal cord, the external colour depends on the level:
Cervical and Lumbar Regions
In the cervical (neck) and lumbar (lower back) regions, the external colour is typically greyish white. These regions of the spinal cord have abundant grey matter which gives it the darker greyish colour externally.
Thoracic Region
The thoracic (chest) region appears more white from the outside. This is because it has a higher proportion of white matter tracts internally.
White Matter vs. Grey Matter
The different colours seen externally correspond to the internal structure of the spinal cord:
- Grey matter – Contains neuron cell bodies, neuroglial cells, capillaries. Responsible for processing information.
- White matter – Contains axons with myelin sheaths. Responsible for transmission of signals.
The grey matter is concentrated near the centre of the spinal cord, while the white matter surrounds it and travels up and down the length of the spinal cord. The varying proportions of grey and white matter at different spinal levels contribute to the external colouration.
Blood Supply
The ample blood supply to the spinal cord also influences its colour:
- Anterior spinal artery – Runs down the anterior surface.
- Two posterior spinal arteries – Run down the posterior surface.
- Segmental arteries – Branch off regularly along the length.
The high vascularity produces a pinkish hue underlying the greyish white or white external colour.
Changes in Pathological Conditions
Certain pathological conditions can alter the typical external colour of the spinal cord:
- Reddish spinal cord – Subarachnoid hemorrhage due to trauma.
- Grey translucent spinal cord – Postmortem change.
- Brown discoloration – Vitamin B12 deficiency.
However, in most cases, the healthy spinal cord maintains its greyish white or white external colour depending on the region.
Significance of Spinal Cord Colour
The external colour of the spinal cord provides information about its:
- Composition
- Blood supply
- Overall health and function
For example, a loss of the typical spinal cord coloration may indicate an underlying pathological process disrupting the normal anatomy.
Conclusion
In summary, the external colour of the healthy human spinal cord varies somewhat based on the region:
- Cervical and lumbar – Greyish white colouration
- Thoracic – More white in appearance
This correlates with the internal proportion of grey matter and white matter. The colour is also influenced by the extensive vascular supply. Significant deviations from the typical external spinal cord colour can signify injury or illness. Recognizing the healthy appearance provides key insights into spinal cord anatomy, physiology, and pathology.
| Spinal Cord Region | Typical External Colour | Reason for Colour |
|---|---|---|
| Cervical | Greyish white | Higher proportion of grey matter internally |
| Thoracic | More white | Higher proportion of white matter tracts |
| Lumbar | Greyish white | Higher proportion of grey matter |
References
- Kayalioglu, G. (2009). The Spinal Cord: A Review of Functional Neuroanatomy. Neuroanatomy (Oct 2009). https://doi.org/10.5772/6743
- Patestas, M.A., & Gartner, L.P. (2016). A textbook of neuroanatomy. John Wiley & Sons.
- Standring, S. (2016). Gray’s anatomy: the anatomical basis of clinical practice. Elsevier.
- Larsen, W.J. (2001). Human embryology (3rd ed.). Churchill Livingstone.
- Milhorat, T.H., Capocelli, A.L., Anzil, A.P., Kotzen, R.M., & Milhorat, R.H. (1995). Pathological basis of spinal cord cavitation in syringomyelia: analysis of 105 autopsy cases. Journal of Neurosurgery, 82(5), 802-812.