The true jelly throughout is termed nucleus pulposus and it is encompassed by the annulus. It has high proteoglycan content and plays a role in retaining water within the disc
The annulus fibrosus is the lamellar layer that surrounds the nucleus pulposus and is rich in collagen fibers.
Disc herniation is defined as focal displacement of disc material < 25% Of the disc circumference, outside the boundaries of the intervertebral disc space.
Uncontained herniated discs do not have the annulus covering, whilst contained herniated discs do. Learn more about the differences between Contained and Uncontained herniated discs, the protrusions have a smooth margin in the case of contained herniations.
The term migration denotes disc material that has moved away from the site of extrusion, regardless of whether it is fragmented.
The term sequestration means that the lost disc material is no longer continuous with the parent disc.