Spinal discs are made of an extremely strong outside network of annular fibers and have a softer, more spongy, inner material. Think of some of the toughest gristle you find on a steak, that is similar to the consistency and toughness of those annular fibers that make up the outer portion of a disc. These fibers are anchored to the vertebra above and below each disc and allow and control movement of the spinal segments while also providing shock absorption and protection of the delicate spinal cord, vertebral nerves and vessels.
When the vertebrae above and below are not in proper alignment or are restricted in movement, shearing forces work on those fibers. Over time this shear causes them to become damaged, weakened and they sometimes tear. When this happens, the inner soft material may bulge against the weakened areas or actually leak through the torn portion of disc, causing a disc herniation, but not a slipped disc.
While surgery may be required in certain cases to remove the inner contents that pushed through the other wall of the disc, most of the time restoring the movement and correcting the alignment of the vertebra above and below through chiropractic care and non-surgical spinal decompression will stop continued damage and allow the disc to heal.