Bodies of two vertebrae are attached to each other by fibrocartilages, for example, intervertebral disc (or intervertebral fibrocartilage) and two ligament links.
The disc is the thickest in the lumbar part of the spine 15-20 mm, becoming thinner up the cervical part.
Discs consist of a strong outer annulus fibrosus which surrounds the soft inner nucleus pulposus.
The soft nucleus behaves as an elastic bowl that a vertebra leans on and moves in all directions.
The soft nucleus always moves to the side of the stretched part of the annulus fibrosus. It moves in the direction opposite of the direction the spine moves in.
With sudden moves or excessive use of force, the soft nucleus mat deforms the annulus fibrosus creating discus hernia. This usually happens in the lumbar part of the spine.
