Blue = Schwann cell,  pink = nucleus of Schwann cell,  yellow = axon of a peripheral nerve

Schwann cells are the main supporting cells (glia cells) of the Peripheral Nervous System. Similar to the oligodendrocytes in the CNS, the purpose of the Schwann cell is to produce a fatty insulating blanket of myelin. The myelin sheath is wrapped around the axon in a fashion similar to rolling a cinnamon bun, creating concentric layers called lamellae. The purpose of the myelin sheath is to increase the speed of impulses across the axon, similar to the insulation around an electric wire. Unlike electric wires that have continuous insulation, gaps exist between the multiple blankets of myelin. These gaps, known as Nodes of Ranvier, allow the impulse to “jump” from node to node, increasing the impulse’s speed even more.

This Daily Doodle captures the interdependent relationship between the Schwann cell and the peripheral nerve axon. Both the axon and the Schwann cell depends on each other for support and development. If the axon is destroyed, the Schwann cell will begin to de-differentiate and if the Schwann cells are destroyed, the axon will begin to degrade.

Pathologies of Schwann cells, which will be covered in other Daily Doodles, include:

• Guillain-Barré syndrome (GBS)
• Charcot-Marie-Tooth disease (CMT)
• Chronic inflammatory demyelinating polyneuropathy (CIDP)
• Schwannomatosis

References:

1. A. Verkhratsky and A. Butt. “Glial Neurobiology”. John Wiley & Sons, Aug 20, 2007

“Bundles of Love” Medical Daily Doodle by Michiko Maruyama