Clefts of Schmidt-Lanterman are best described as which structure?

Clefts of Schmidt-Lanterman are best described as which structure?

• A. Nodes of Ranvier
• B. Clefts of Schmidt-Lanterman
• C. Epineurium
• D. Perineurium

Answer: (B)

Schmidt-Lanterman clefts are cytoplasmic channels within the myelin sheath of peripheral nerves, formed by Schwann cell cytoplasm that remains between the myelin lamellae. These non-compact areas create small, irregular pockets that traverse the sheath and allow metabolic exchange between the axon and the Schwann cell, helping to maintain myelin integrity. This sits in contrast to nodes of Ranvier, which are gaps between myelin segments rich in voltage-gated Na+ channels for saltatory conduction; the epineurium is the outer connective tissue covering the entire nerve, and the perineurium surrounds individual nerve fascicles. So, the description as cytoplasmic channels within the myelin sheath is the best fit.

Schmidt-Lanterman clefts are cytoplasmic channels within the myelin sheath of peripheral nerves, formed by Schwann cell cytoplasm that remains between the myelin lamellae. These non-compact areas create small, irregular pockets that traverse the sheath and allow metabolic exchange between the axon and the Schwann cell, helping to maintain myelin integrity.

This sits in contrast to nodes of Ranvier, which are gaps between myelin segments rich in voltage-gated Na+ channels for saltatory conduction; the epineurium is the outer connective tissue covering the entire nerve, and the perineurium surrounds individual nerve fascicles. So, the description as cytoplasmic channels within the myelin sheath is the best fit.