A lumbar disc herniation (herniated disc) is a rupture and/or bulge of an interverterbral disc in the low back. The intervertebral disc is a complex spongy structure which consists of a central sticky gelatinous portion, the nucleus, and an outer fibrous ring of tissue, the annulus. These discs are found along the entire spine from the neck all the way down to the lowest part of the back. The function of this disc is to permit motion of the spine while also acting as a shock absorber and connecting link between each vertebral body. The outer layer, the annulus, may actually tear and result in extrusion or bulge of the inner part of the disc, the nucleus. This is called a disc herniation. The nerve may become irritated either as a result of chemical reaction to an injured disc and/or to compression from the herniated disc itself. The space in which nerves normally sit is quite small and there is not much free space. The symptoms from this irritation can range from numbness, tingling and pain to bladder dysfunction, weakness and even partial paralysis. The particular area of the body which is affected depends upon which nerve is being irritated by the herniated disc.
Complete Talk on slip disc and Sciatica by Dr Pramod Saini