Vertebral canal

What is inside the vertebral canal?

The canal space is lined with periosteum. It contains the spinal cord (42–46 cm long and 10–14 mm in diameter), which in adults terminates at the level of the first or second lumbar vertebra.

The structures and spaces of the canal are arranged in layers (from superficial to deep):

• Epidural space (spatium epidurale) is located between the periosteum and the dura mater. It contains adipose tissue and the internal vertebral venous plexus.
• Dura mater of the spinal cord (dura mater spinalis).
• Arachnoid mater of the spinal cord (arachnoidea mater spinalis).
• Subarachnoid space (spatium subarachnoideum) is located between the arachnoid and pia maters.
• Pia mater of the spinal cord (pia mater spinalis) closely adheres to the spinal cord. Its derivative is the denticulate ligament (ligamentum denticulatum), which anchors the spinal cord within the canal.

Blood supply and venous drainage

Inside the vertebral canal (canalis vertebralis), external to the dura mater, lie the internal vertebral venous plexuses (plexus venosi vertebrales interni). They extend from the foramen magnum to the lower end of the sacral canal and are divided into anterior and posterior plexuses. The basivertebral veins, coming from the vertebral bodies, drain into the anterior internal plexus. The internal plexuses anastomose with the external ones.

Arterial blood supply is provided by radicular arteries (aa. radiculares), which enter the vertebral canal together with the anterior and posterior spinal roots. Because the spinal cord grows more slowly than the vertebral column during embryogenesis (ascensus medullae spinalis), the level at which the artery penetrates the spinal cord lies higher than its point of origin from the aorta. This accounts for the oblique (ascending) course of the arteries within the canal.

Innervation of canal structures

The meninges and tissues of the canal itself are innervated by the meningeal branch (r. meningeus). It branches off the spinal nerve, loops back into the vertebral canal, and innervates:

• The dura mater;
• The periosteum;
• Blood vessels, as it contains sympathetic fibers.

Clinical significance

Space-occupying lesions in the vertebral canal lead to compression of neural structures:

• Intervertebral disc herniation: prolapse of a free fragment (sequestrum) into the canal causes massive compression. At the lumbar level, this leads to acute cauda equina syndrome, which manifests as lower paraparesis, decreased sensation in the anogenital region, and overflow urinary incontinence.
• Tumors: can be extradural or intradural. Schwannomas often grow in a "dumbbell" shape—originating in the intervertebral foramen and growing bidirectionally: inside and outside the canal. Lateral compression of the spinal cord leads to Brown-Séquard syndrome. Advanced skin cancers (T4/T4b stages) can also invade the epidural space of the canal.
• Downward (tonsillar) herniation: in mass lesions of the posterior cranial fossa, the cerebellar tonsils may shift downward through the foramen magnum into the vertebral canal, causing compression of the caudal brainstem.

Class and exam questions

What else to study on this topic

• The spinal cord and its segmental apparatus
• Spinal meninges and epidural space
• Blood supply to the spinal cord (Artery of Adamkiewicz)
• Cauda equina syndrome and compression syndromes

Other topics in the "Anatomical Structures" section

Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.