PERIPHERAL NERVE: Normal features

Toluidine Blue stained plastic section	Electron micrograph: From Robert E Schmidt MD
Nerves from adults Note 3 populations of axons • Large with thick myelin sheath • Intermediate size with thinner myelin sheath • Small, unmyelinated axons
Nerve from child Axons are smaller & myelin sheaths thinner.	Nerve from neonate Few axons are myelinated. Fibroblasts are prominent.
Electron micrograph (Robert E Schmidt MD)	Electron micrograph: (Robert E Schmidt MD)
Unmyelinated axons	Node of Ranvier Non-myelinated axon segment   between 2 Schwann cells Anatomy Axonal diameter reduced Increased organelle density Usually ~ 1 μm in length Myelin (Schwann cell) loops surround axon