What is the vertebral canal and what does it contain?

The vertebral canal is a long cavity formed by the stacked vertebral foramina, running from the foramen magnum to the sacral canal. It contains the spinal cord, its spinal meninges (dura, arachnoid, and pia mater), and the epidural space with fat and blood vessels.

What is the epidural space and what structures are found there?

The epidural space is located between the spinal dura mater and the walls of the vertebral canal. It contains loose areolar tissue and fat, spinal arteries, and the internal vertebral venous plexus.

How does the vertebral venous plexus function and why is it clinically significant?

The vertebral venous plexus includes internal and external networks that drain blood from the spine. These veins are valveless, allowing bidirectional flow, which can enable metastasis (e.g., from prostate cancer to the skull).

What are the spinal meninges and their key features?

The spinal meninges are three protective layers around the spinal cord: Dura mater extends from the foramen magnum to S2, with sleeves over spinal nerves. Arachnoid mater is a thin layer ending at S2, with the subarachnoid space below containing CSF. Pia mater is a vascular membrane closely attached to the cord, with extensions like the filum terminale.

What is the filum terminale and how is it structured?

The filum terminale is a thin fibrous strand extending from the conus medullaris to the coccyx. It is divided into two parts: Internum is about 15 cm long, located within the dural sac, and externum is about 5 cm long, located outside the dura mater.

Why is a lumbar puncture performed at the L3–L4 level?

A lumbar puncture is performed at the L3–L4 level to access the lumbar cistern in the subarachnoid space, which contains cerebrospinal fluid (CSF). This level is safe because the spinal cord typically ends around L1, minimizing risk of injury.

What is the difference between spinal and epidural anesthesia?

In spinal anesthesia, the anesthetic is injected directly into the subarachnoid space. In epidural anesthesia, the drug is injected into the epidural space without piercing the dura mater.

Vertebral Canal & Spinal Meninges – Anatomy & Lumbar Cistern

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