Spinal Cord Anatomy

Introduction

• Spinal cord originates from brainstem, pass through foramen magnum and continues distally through cervical and thoracic regions of the spinal column before terminating as a tapering structure known as the conus medullaris. Spinal cord ends at the level of L1 or L2 in adults and L3 in children.

• The cross-sectional structure of spinal cord consists of grey matter and white matter.

• Gray matter which is organized as an H- shaped body of cell bodies. The anterior horn (motor nuclei) and the dorsal horn (sensory nuclei) of both sides are connected with grey commissure.

• White matter which is organized into anterior, posterior and lateral columns (thoracic region only) comprise many ascending and descending tracts (Fig. 1)

• Spinal cord comprises of the 31 total nerve root sections (8 cervical, 12 thoracic, 5 lumbar, 5 sacral, and 1 coccygeal).

• Nerves from the lower spinal segment exit terminal to the conus medullaris and form the cauda equine.

Meninges and Spaces

• Three membranes that cover the spinal cord from outward to inward (dura mater, arachnoid mater and pia mater) are known as meninges.

• The space between the bony framework of the spinal vertebral column and the thick dura mater surrounding the spinal cord is known as epidural space.

• The space between the dura mater and pia mater is known as subarachnoid space (contains CSF).

Vertebral column

• An adult spine has S-shaped curve, cervical as well as lumbar regions has concave with more mobility, besides thoracic plus sacral regions have a convex curve. Consisting of 33 vertebrae (7 cervical, 12 thoracic, five lumber, five bones fused to form the sacrum and four fused to form coccyx).

• Vertebrae consist of the body (anterior) and arch (posterior) surrounding a vertebral foramen (contain spinal cord and meninges). The vertebral arch is made up of pair of pedicles (sides) and laminae which gives the spinous process at their junction.

Intervertebral disc

• Between two vertebral bodies (except C1 and C2), the discs which serves as the support for spine. It is covered with the annulus that surrounds nucleus pulposus. It functions as the shockwave absorbers for bones of spine.

Blood supply

• Anterior spinal arteries (anterior 2/3rd)

• Posterior spinal arteries (posterior 1/3rd)

• Segmental arteries reinforce the anterior and posterior arteries at each intervertebral foramen

Figure 1: Ascending and Descending Tracts of Spinal Cord

Further Reading

• Adigun OO, Reddy V, Varacallo M. Anatomy, Back, Spinal Cord. [Updated 2021 Aug 4]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2021 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK537004/

• Khan, Yusuf & Lui, Forshing. (2020). Neuroanatomy, Spinal Cord.

Bibliography

• Splittgerber, R. (2019). Snell's Clinical Neuoanatomy (C. Taylor Ed. 8th ed.). Philadelphia: Wolters Kluwer.

• Mitchell, and Henry Gray. Gray's Anatomy for Students. Philadelphia: Elsevier/Churchill Livingstone, 2005.