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.
Medical Definition of Flat feet. Flat feet: Absence of an arch in the sole of the foot that causes the foot to lie flat when the person is standing. All babies have flat feet because their arches are not yet built up (and their feet tend to be plump). This condition may persist into adulthood, or an arch may form as the child grows.