Spinal Anatomy 101 – Spinal Cord and Nerves

Stanley Hoppenfeld, MD and
Michael S. Zeide, MD
illustrations by James Capizzuto, Orthopaedic Dictionary, 1994.)

The spine is one of the most important components of the human architecture. It is composed of bones, joints, muscles, ligaments and nerve structures.

The following represent many of the important nerve structures found in the spine.

Spinal Cord

The portion of the central nervous system enclosed in the vertebral column. It consists of nerve cells and bundles of nerves connecting all parts of the body to the brain. The spinal cord contains a core of gray matter surrounded by white matter; it extends from the medulla oblongata at the upper border of the atlas to the level of the second lumbar vertebra. Below the first lumbar vertebra, the canal is occupied by a leash of lumbar, sacral, and coccygeal nerve roots termed the cauda equina. The spinal nerves emerge from the spinal cord in pairs: eight cervical, twelve thoracic, five lumbar, five sacral, and one pair of coccygeal nerves. The cord has two enlargements, cervical and lumbar, that correspond to the nerve supply of the upper and lower limbs. The spinal cord is enveloped by three membranes – the dura, the arachnoid, and the pia mater; these are direct continuations of those surrounding the brain.

Anterior Sacral Foramina	Figure 1
Circular openings on either side of the midline of the front of the sacrum through which pass the anterior branches of the sacral nerves.

Arachnoid Mater or Arachnoid

The delicate membrane of the brain and spinal cord between the dura and pia maters.

Figure 2

Conus Medullaris The distal termination of the spinal cord proper in an adult, usually at the T12 = L1 level.

Dermatomes The area of skin supplied by the fibers of a single spinal root.

Figure 3

Dura Mater or Dura

The outermost of the three membranes covering the spinal cord and the brain. It is the toughest and most fibrous of the membranes.

Epidural

The outermost of the three spaces covering the brain and spinal cord. It is located on or over the dura mater. May be referred to as the Epidural Space.

Figure 4

Intervertebral Foramen

Lumbosacral Plexus

The combination of all the ventral primary divisions of the lumbar, sacral, and coccygeal nerves. Usually referred to as separate lumbar and sacrococcygeal plexi. The lumbar and the sacral plexi supply the lower limb. The sacral nerves also supply the perineum through the pudendal plexus and the coccygeal area through the coccygeal plexus.

Meninges

Any one of the three membranes (the dura mater, the arachnoid, and the pia mater) that encloses the central nervous system.

Neural Arch

Figure 5

Sacral Nerves

The five pairs of spinal nerves that emerge from the spinal column in the sacrum. The sacral nerves carry sensory and motor fibers and to and from both the upper and lower leg and from the anal and genital regions.

Figure 6

Sacral Plexus A nerve plexus (a network of interlacing nerves) arising from the lumbosacral trunk and ventral branches of the first four sacral spinal nerves.

Spinal Nerve Root

Neural structures that exit the spinal cord anteriorly and posteriorly, combining to form a single spinal nerve.

Transverse Foramen	Figure 7

Credits

(Material provided by Stanley Hoppenfeld, MD and Michael S. Zeide, MD, illustrations by James Capizzuto, Orthopaedic Dictionary, 1994.)

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