In the spinal cord, the myelin sheath is formed by?

Appeared in: DSSSB Public Health Nurse - 2015

Explanation

The question asks which cell forms the myelin sheath in the spinal cord.
The spinal cord is a key component of the Central Nervous System (CNS).
Oligodendrocytes are the specific type of glial cells responsible for producing and maintaining the myelin sheath around axons within the CNS.
As shown in the provided diagram and confirmed by neuroanatomy, a single oligodendrocyte can extend its processes to myelinate multiple axons simultaneously.
Therefore, oligodendrocytes are the correct answer for myelination in the spinal cord.

Option A: Schwann cells are responsible for myelination, but they are located in the Peripheral Nervous System (PNS), which includes all the nerves outside of the brain and spinal cord.
Option C: Osteocytes are mature bone cells found within the lacunae of bone tissue. They are involved in bone maintenance and have no function related to the nervous system or myelination.
Option D: Microglia are the resident immune cells (macrophages) of the CNS. Their primary role is to respond to injury and infection by clearing cellular debris and pathogens, not to form myelin.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Cellular basis of myelination in the Central Nervous System (CNS) as background academic context rather than a clinical decision trigger.
Damage to oligodendrocytes and the subsequent loss of myelin in the CNS is the hallmark of Multiple Sclerosis (MS). Nurses play a vital role in managing MS symptoms, administering disease-modifying therapies, and providing patient education on preventing relapses.
What if? If the patient had Guillain-Barré syndrome instead of MS, the pathology would involve the Schwann cells in the PNS. This leads to ascending muscle weakness and paralysis, requiring different nursing priorities, such as respiratory monitoring and management of autonomic dysfunction.

How to Approach the Question

First, identify the key terms in the question: 'spinal cord' and 'myelin sheath'.
Recognize that the 'spinal cord' is part of the Central Nervous System (CNS), along with the brain.
Recall the different types of glial cells and their primary functions.
Differentiate between myelination in the CNS and the Peripheral Nervous System (PNS).
Associate Oligodendrocytes with CNS myelination and Schwann cells with PNS myelination.
Eliminate options that are unrelated to the nervous system (Osteocytes) or have a different function within the CNS (Microglia).

Concept Tested & Keywords

Concept Tested: Cellular basis of myelination in the Central Nervous System (CNS).
Stem keywords: spinal cord, myelin sheath
Lead-in keywords: formed by
Negative lead-in flag: false

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E6 Anatomy Grays 43e Vol 1 Part 1 pp. 92-94, 85-87

E6 Medicine Harrison 22e Part 2 p. 1301-1303

Practise the full DSSSB Public Health Nurse - 2015

Attempt every question from this paper in a timed mock, then review the full solution for each one.