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.
Flat feet/fallen arches. Having flat feet is also known as having fallen arches, and means the arches of the feet are low or there are no arches. Flat feet may not cause any pain or problems, but strain can be caused to muscles and ligaments making it painful when walking.