The Anatomy of the Spinal Cord

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This webpage presents the anatomical structures found on spinal canal.

The Spinal Cord and Its Functions

The brain and spinal cord are part of the central nervous system (CNS)(1). The CNS is responsible for bodily functions, such as motor skills, sensory responses, and cognitive functions(2).

There are three specific spinal cord functions: motor, sensation, and autonomic control(3).

Motor functions include the body’s reflexes or reactions to a specific stimulus and patterned movements of the body(4). These functions allow stretch reflexes and several joints’ patterned responses.

The spinal cord’s sensory processing functions constitute the ability to initiate sensory modalities, like pain, touch, temperature, and proprioception (the body’s ability to know its position)(5).

Autonomic responses, like digestion, heart rate, urination, and body temperature, are also associated with the spine’s anatomical function.

The spinal cord is the link between the brain and all the body’s nerves(6). It stretches up to 40cm to 50cm with a diameter of 1cm to 1.5cm.

The spinal cord encompasses the medulla oblongata (lower part of the brainstem) from the foramen magnum (hole in the base of the skull) to the first or second lumbar vertebrae(7).

There are two consecutive rows of nerve roots in each side of the spinal cord that distally connects to form the spinal nerves(8). These nerves transmit information and signals from the head to the central nervous system(9).

This bone structure is divided into cervical (C), thoracic (T), sacral (S), and lumbar (L) regions(10). Each of these regions is divided into 31 segments that innervate a specific spinal nerve(11).

There are five segments in the lumbar and sacral spines, 12 segments in the thoracic spine, eight segments in the cervical spine, and one coccygeal nerve(12).

Each of these segments or vertebrae is separated by intervertebral discs and extends into a hollow longitudinal passage called the spinal canal(13).

Cervical Spine

The cervical spine is a flexible spinal region located in the body’s neck area(14). It has a 70 degrees extension, 80 to 90 degrees flexion, and 90 degrees rotation on each side(15).

The atlas, the first cervical vertebra attached to the skull, supports the whole of the head(16). Meanwhile, the C2 vertebral segment or the axis carries the weight of the head(17).

Thoracic Spine

The thoracic spine is the most rigid part of the spinal cord due to its rib cage, which protects the lungs and heart(18). This part of the spinal column attaches to the arm, shoulder, and trunk muscles(19).

The thoracic spine is located in the middle part of the spinal cord, and each of its segments is numbered from T1 to T12(20).

These vertebral segments are larger than the cervical spine segments and grow more prominent towards the lumbar vertebrae due to the weight support function of the lower vertebrae(21).

Lumbar Spine

This part of the spine is located at the lower part of the back(22). The lumbar vertebrae are the largest among the vertebrae in the spine because they support the body’s weight(23).

The lumbar spine can absorb axial forces from the trunk, head, and neck(24). This part of the spine also permits flexion, rotation, side bending, and extension(25).

Sacral Spine

The sacral spine or sacrum has five fused bones formed in an inverted triangle that is anteriorly concave and posteriorly convex(26).

The superior part of the sacrum, also called the sacral promontory, articulates with the fifth lumbar vertebrae that form the lumbosacral joints. These joints are assisted by the lumbosacral and iliolumbar ligaments(27).

The sacrum connects with the coccyx (the triangular bone at the base of the spine) through the coccygeal and sacral cornua(28).

Clinical Significance of the Spinal Cord

It is crucial to take care of the spinal cord as it is responsible for essential functions, such as walking, standing, and transmitting body weight. Most of the common causes of spinal cord disorders are(29):

  • Infections
  • Physical injuries
  • Tumors
  • Fractured bones
  • Blocked blood supply

Physicians examine the spinal column and base their diagnosis through imaging tests, such as magnetic resonance imaging (MRI), radiography or X-ray, and computed tomography (CT) scan(30).

Abnormal sensations, loss of bladder and bowel control, and weak or paralyzed muscles are some of the problematic repercussions of spinal cord disorders and injuries(31).

One of the spinal disorders is spinal stenosis. It happens when the spaces within the spine narrow and put pressure on the spinal nerves. This condition may happen in the cervical and lumbar area of the spinal cord(32).

Patients suffering from spinal stenosis may experience pain, numbness, tingling sensations, and muscle weakness(33).

References

  • Harnsberger HR, Osborn AG, Ross JS, Moore KR, Salzman KL, Carrasco CR, Halmiton BE, Davidson HC, Wiggins RH. Diagnostic and Surgical Imaging Anatomy: Brain, Head and Neck, Spine. 3rd ed. Salt Lake City, Utah. Amirsys. 2007.
  • Bourjat P, Veillon F. Imagerie radiologique tête et cou. Paris, Vigot. 1995.
  • Gouazé A, Baumann JA, Dhem A. Sobota. Atlas d’Anatomie humaine. Tome 3. Système nerveux central, système nerveux autonome, organe des sens et peau, vaisseaux et nerfs périphériques. 1er éd. Paris, Maloine. 1977.
  • Kahle W, Cabrol C. Anatomie. Tome 3: Système nnerveux et organe des sens. 1er éd. Paris, Flammarion. 1979.
  1. University of Pittsburgh School of Medicine Neurological Surgery, (n.d.), About The Brain and Spinal Cord, retrieved from https://www.neurosurgery.pitt.edu/centers/neurosurgical-oncology/brain-and-brain-tumors/about
  2. IBID.
  3. Nógrádi A, Vrbová G. Anatomy and Physiology of the Spinal Cord. In: Madame Curie Bioscience Database [Internet]. Austin (TX): Landes Bioscience; 2000-2013. Available from: https://www.ncbi.nlm.nih.gov/books/NBK6229/
  4. Ibid.
  5. Ibid.
  6. University of Iowa Hospitals and Clinics, How Does the Spinal Cord Work?, retrieved from https://uihc.org/health-topics/how-does-spinal-cord-work
  7. McGovern Medical School, Anatomy of the Spinal Cord, retrieved from https://nba.uth.tmc.edu/neuroscience/m/s2/chapter03.html
  8. Ibid.
  9. Ibid,
  10. Ibid.
  11. Ibid.
  12. Ibid.
  13. American Association of Neuriological Surgeons, (n.d), Cervical Spine, retrieved from https://www.aans.org/en/Patients/Neurosurgical-Conditions-and-Treatments/Cervical-Spine
  14. Ibid.
  15. Swartz, E. E., Floyd, R. T., & Cendoma, M. (2005). Cervical spine functional anatomy and the biomechanics of injury due to compressive loading. Journal of athletic training, 40(3), 155–161.
  16. Ibid.
  17. Ibid.
  18. Evans, R. C., ( 2009), Chapter Seven - Thoracic Spine, retrieved from https://www.sciencedirect.com/science/article/pii/B9780323045322500122
  19. Ibid.
  20. Papadopoulos, S. M., and Fessler, R, G., (2005), Thoracic Spine, retrieved from https://www.sciencedirect.com/sdfe/pdf/download/eid/3-s2.0-B9780443066160500286/first-page-pdf
  21. Ferng, A., (October 2020), Thoracic Vertebrae, retrieved from https://www.kenhub.com/en/library/anatomy/thoracic-vertebrae
  22. American Association of Neurological Surgeons, (n.d.), Lumbar Spinal Stenosis, retrieved from https://www.aans.org/en/Patients/Neurosurgical-Conditions-and-Treatments/Lumbar-Spinal-Stenosis
  23. Ferng, A., (September 2020), Lumbar Verterbrae, retrieved fromhttps://www.kenhub.com/en/library/anatomy/lumbar-vertebrae
  24. Sassack B, Carrier JD. Anatomy, Back, Lumbar Spine. [Updated 2020 Aug 10]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2020 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK557616/
  25. Ibid.
  26. Sattar MH, Guthrie ST. Anatomy, Back, Sacral Vertebrae. [Updated 2020 Jul 31]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2020 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK551653/
  27. Ibid.
  28. Ibid.
  29. Rubin, M., (February 2020), Overview of Spinal Cord Disorders, retrieved from https://www.msdmanuals.com/home/brain,-spinal-cord,-and-nerve-disorders/spinal-cord-disorders/overview-of-spinal-cord-disorders
  30. Ibid.
  31. Ibid.
  32. Mayo Clinic, (n.d.) Spinal Stenosis, retrieved from https://www.mayoclinic.org/diseases-conditions/spinal-stenosis/symptoms-causes/syc-20352961#:~:text=Spinal%20stenosis%20is%20a%20narrowing,stenosis%20may%20not%20have%20symptoms.
  33. Ibid.

References

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