The vertebral column is made up of thick cubical bones which are mounted on top of one another to form a tall structure eg., bricks mounted on top of each other.
the vertebral coloumn bones stacked up one on top of the other!
In between these bricks lies the soft cushion known as the inter vertebral disc.
A soft rubber like cushion is situated between the bricks or bones
A soft rubber like cushion is situated between the bricks or bones
An intervertebral disc is made up of a rubber like material, it has a central pulp(nucleus pulposus) surrounded by circular fibrous tissue called annulus fibrosus. shown below fig 1 fig 2 and fig 3
The function of the disc is to act as a shock absorber and joint between the two vertebral bones , as the person jumps, runs walks or lifts weight the disks absorb the shocks, also when we twist the waist. the disks acting as the joint around which the bones pivot.
The disk prevents the vertebral bodies from coming in contact with each other.
On top of the vertebral column lies the persons head and below, the vertebral column rests on the sacrum. The weight of the head causes the vertebral column to be compressed between the head and the sacrum. as we walk or run the forces generated travel up via the ankle joint, knee joint, hip joint and reach the sacrum bone, from here the forces collide against the vertebral coloumn(lumbar vertebrae)
fig 3
These forces can cause damage to the body and they need to be dampened.
To prevent compression and friction between the vertebrae the 'shock absorber disk' comes into action.
As the person jumps vertebrae, one on top of the other are pressed against each other, the pressure within the central pulp rises and the pulp tries to push out against the annulus fibrosus fig 4, The annulus counters this by tensing around the pulp! This mechanism contains the pulposus within the annulus! and prevents the pulposus from extruding out of the annulus and the vertebrae from coming in contact with each other.
fig4 fig 5 fig 6
If (1) the pressure built up within the annulus is too great or (2) if the annulus has hardened due to degeneration or simply dried up(dessicated) or (3) if the vertebral column is twisted in an abnormal fashion or pulled violently by the ligaments and muscles attached to it, then the annulus bulges out fig 6 or it gives way and the pulp finds its way outside called extrusion fig 7,8,9, resulting in failure of the shock absorber mechanism and giving rise to the phenomenon known as the slipped disk.
If (1) the pressure built up within the annulus is too great or (2) if the annulus has hardened due to degeneration or simply dried up(dessicated) or (3) if the vertebral column is twisted in an abnormal fashion or pulled violently by the ligaments and muscles attached to it, then the annulus bulges out fig 6 or it gives way and the pulp finds its way outside called extrusion fig 7,8,9, resulting in failure of the shock absorber mechanism and giving rise to the phenomenon known as the slipped disk.
When the pulposus bulges into the spinal canal or the pulp breaks out of the annulus and enters the vertebral canal to come in contact and compress the spinal cord it is known as herniation/ prolapse of an inter vertebral disc.
extrusion of the pulposus fig 7,,8,9.
1 comment:
This is so well written. Explains clearly and lucidly. It's of a great help. Thank you Doc.
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