The dural sheath around the spinal cord is formed from which of the following?

• A. Pia mater
• B. Periosteal layer of the dura mater
• C. Meningeal layer of the dura mater
• D. Arachnoid mater

Answer: (C)

Verified step by step guidance

1. Understand the structure of the meninges, which are protective layers surrounding the brain and spinal cord. The meninges consist of three layers: the dura mater (outermost), arachnoid mater (middle), and pia mater (innermost).
2. Recognize that the dura mater itself has two layers: the periosteal layer (closely attached to the skull in the cranial cavity) and the meningeal layer (which extends down to form the dural sheath around the spinal cord).
3. Clarify that the periosteal layer of the dura mater is only present in the cranial cavity and does not extend to the spinal cord. Therefore, it cannot form the dural sheath around the spinal cord.
4. Understand that the meningeal layer of the dura mater separates from the periosteal layer in the spinal region and forms the dural sheath, which surrounds and protects the spinal cord.
5. Eliminate other options: The pia mater is the innermost layer directly adhering to the spinal cord, and the arachnoid mater is the middle layer, neither of which forms the dural sheath. Thus, the correct answer is the meningeal layer of the dura mater.