Kyphosis (right) vs. normal spinal column (left).

Lateral view of an adult female flexing her back.

Normal myelin of CNS in multiple sclerosis.

Sagittal view of the spinal column with a normal spinal cord.

Lateral view of the skull and neck muscles bent to the back.

Graphic depiction of myelin of CNS in four stages of multiple sclerosis: normal myelin (top), destruction and removal of myelin sheath (middle two images) and remyelination and subsequent scarring (bottom).

Lateral view of male head and neck bent to the back.

Lateral view of adult male figure as he leans back and bends forward to demonstrate flexion and extension of spine.

Three lateral images of male head and neck featuring skull and neck muscles as head is held stationary (top), bent to the back (middle), and to the front (bottom).

Back flexion, normal