Nerve fiber = multicellular, containing both an axon and surrounding myelin sheath. The axon comes from a single neuron, but the myelin sheath is made by a train of many myelinating Schwann cells. In the case of unmyelinated axons, the unmyelinated fiber shares each Schwann cell with several other unmyelinated axons.
Flat feet (pes planus) occur when a child has no arch in their foot. Because an arch does not form, the foot appears to turn to the outside. Children with out-toeing due to flatfeet will rarely experience pain symptoms will not require treatment.
The exact cause is unknown. 1  However, some experts believe the following may play a role in the development of this condition: 2  Abnormal positioning of toes. 3  Flat feet. 4  Forefoot problems, including bunions and hammer toes. 5  High foot arches. 6  Tight shoes and high heels.