Intervertebral disc
An intervertebral disc (or intervertebral fibrocartilage) lies between adjacent vertebrae in the vertebral column.
Each disc forms a fibrocartilaginous joint (a symphysis), to allow slight movement of the vertebrae, and acts as a ligament to hold the vertebrae together. Their role as shock absorbers in the spine is crucial.
There is one disc between each pair of vertebrae, except for the first cervical segment, the atlas. The atlas is a ring around the roughly cone-shaped extension of the axis (second cervical segment). The axis acts as a post around which the atlas can rotate, allowing the neck to swivel.
There are 23 discs in the human spine
: 6 in the neck (cervical region),
12 in the middle back (thoracic region), and
5 in the lower back (lumbar region). For example, the disc between the fifth and sixth cervical vertebrae is designated "C5-6".
Each disc forms a fibrocartilaginous joint (a symphysis), to allow slight movement of the vertebrae, and acts as a ligament to hold the vertebrae together. Their role as shock absorbers in the spine is crucial.
There is one disc between each pair of vertebrae, except for the first cervical segment, the atlas. The atlas is a ring around the roughly cone-shaped extension of the axis (second cervical segment). The axis acts as a post around which the atlas can rotate, allowing the neck to swivel.
There are 23 discs in the human spine
: 6 in the neck (cervical region),
12 in the middle back (thoracic region), and
5 in the lower back (lumbar region). For example, the disc between the fifth and sixth cervical vertebrae is designated "C5-6".
Structure
Discs consist of an outer fibrous ring, the anulus fibrosus disci intervertebralis.
The anulus fibrosus consists of several layers (laminae) of fibrocartilage made up of both type I and type II collagen. Type I is concentrated towards the edge of the ring where it provides greater strength. The stiff laminae can withstand compressive forces.
Inner gel-like center is the nucleus pulposus.
The fibrous intervertebral disc contains the nucleus pulposus and this helps to distribute pressure evenly across the disc.
This prevents the development of stress concentrations which could cause damage to the underlying vertebrae or to their endplates. The nucleus pulposus contains loose fibers suspended in a mucoprotein gel.
The nucleus of the disc acts as a shock absorber, absorbing the impact of the body's activities and keeping the two vertebrae separated.
It is the remnant of the notochord.[1]
The anulus fibrosus consists of several layers (laminae) of fibrocartilage made up of both type I and type II collagen. Type I is concentrated towards the edge of the ring where it provides greater strength. The stiff laminae can withstand compressive forces.
Inner gel-like center is the nucleus pulposus.
The fibrous intervertebral disc contains the nucleus pulposus and this helps to distribute pressure evenly across the disc.
This prevents the development of stress concentrations which could cause damage to the underlying vertebrae or to their endplates. The nucleus pulposus contains loose fibers suspended in a mucoprotein gel.
The nucleus of the disc acts as a shock absorber, absorbing the impact of the body's activities and keeping the two vertebrae separated.
It is the remnant of the notochord.[1]