Why are ganglia and nerves not surrounded by protective structures like the meninges of the central nervous system (CNS)?

• A. Because ganglia and nerves are protected by bone instead of meninges.
• B. Because the meninges only protect blood vessels, not nervous tissue.
• C. Because ganglia and nerves are located deep within the brain and spinal cord.
• D. Because ganglia and nerves are part of the peripheral nervous system, which is not enclosed by the meninges.

Answer: (D)

Verified step by step guidance

1. Step 1: Understand the structural differences between the central nervous system (CNS) and the peripheral nervous system (PNS). The CNS includes the brain and spinal cord, which are enclosed by protective meninges and surrounded by bone (skull and vertebrae). The PNS consists of ganglia and nerves, which are located outside of these protective structures.
2. Step 2: Recognize the role of meninges. Meninges are specialized protective layers (dura mater, arachnoid mater, and pia mater) that surround the CNS to provide physical protection and support, as well as to contain cerebrospinal fluid (CSF). These structures are not present in the PNS.
3. Step 3: Note the anatomical location of ganglia and nerves. Ganglia are clusters of neuron cell bodies, and nerves are bundles of axons. Both are part of the PNS and are located outside the brain and spinal cord, making them distinct from the CNS structures protected by meninges.
4. Step 4: Understand the functional distinction. The PNS is responsible for transmitting signals between the CNS and the rest of the body. Since ganglia and nerves are not enclosed by bone or meninges, they rely on other protective mechanisms, such as connective tissue coverings (epineurium, perineurium, and endoneurium).
5. Step 5: Conclude that the correct answer is based on the anatomical and functional separation of the CNS and PNS. Ganglia and nerves are part of the PNS, which is not enclosed by meninges, unlike the CNS.