Intervertebral disc: definition, function — Explained Simply — Profphysio
The intervertebral disc (intervertebral fibrocartilage) as its name appears is the part that lies between every two vertebrae of the spine.
The intervertebral disc consists of 2 main components which are the outer fibrous ring (annulus fibrosus), which surrounds the inner component in the center of the intervertebral disc (the nucleus pulposus).
The function of the nucleus pulposus of the disc is to distribute hydraulic pressure in all directions within each intervertebral disc under compressive loads like bodyweight, lifting objects or other external forces.
But the nucleus pulposus consists of large vacuolated notochord cells, small chondrocyte-like cells, collagen fibrils, and other types of materials which provide the disc with the strength and durability and maintain the Intervertebral disc connected to every vertebra above and below.
As one of the most important functions of the intervertebral disc is the shock absorption, So when you be exposed to direct or indirect trauma (external force) it acts like a shock absorber which can decrease the impact of the trauma or force on your spine.
The vertebral column consists of 33 vertebrae divided into 5 regions, which are the:
Cervical spine (7 vertebrae)
Coccyx spine (4 fused vertebrae)
The upper 24 vertebrae are separated by the intervertebral discs, but the lower 9 vertebrae which are the sacral and coccyx vertebrae are fused in adults, which makes each region separated without intervertebral disc, so the movement in the lower 9 vertebrae is impossible.
Herniation of the intervertebral disc occurs due to the unbalanced mechanical pressure on the annulus fibrosus may be due to bad posture, bad sudden movements or trauma like in RTA or sudden faulty movement with or without lifting objects (extra weight to your body weight), and therefore causing a tear of annulus fibrosus which allow the nucleus pulposus to exit the intervertebral disc causing pressure on the nerves within the vertebral column.
The intervertebral disc herniation could be sudden or gradual in its onset:
Sudden disc herniation is a force of sudden movement of your body during daily activities or for example sudden sneezing during faulty posture (when there is maximal unbalanced pressure within your spine upon your intervertebral disc), this makes the nucleus pulposus to exit from the weakest point right on time.
Gradual disc herniation could be caused by a gradual bulge or exit of the nucleus pulposus due to bad habits of posture, or in certain sports which need lifting weights.
Symptoms of the intervertebral disc herniation:
- Acute or chronic like in low back pain in case of lumbar disc herniation.
- Sometimes referred pain to the lower limbs (in lumbar disc herniation) or referred pain to the upper limbs (in the cervical disc).
- Paresthesia (decreased sensation) or Numbness over the surface area innervated by the compressed nerve (dermatomes).
- Sometimes decreased muscle tone ( hypotonia).
- Muscles weakness in muscles which innervated by the compressed nerve.
After the age of 40 most of people about 60% of them has degeneration of the intervertebral disc as a normal aging process, which is decrease water and other materials like the proteoglycans in the nucleus pulposus which gives the intervertebral disc it’s durability and softness which make the disc able to do its normal function which is the shock absorption. Also , the annulus fibrosus be weak and susceptible to tear.
Degeneration can cause symptoms like a severe muscle spasm or sometimes contracture in the lumbar or thoracolumbar spine.
Often physiotherapy or surgery are the most common and effective treatment options for the intervertebral disc herniation and to decrease the symptoms the arise from aging degeneration.
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Originally published at https://profphysio.com on February 7, 2020.
