Final answer:
A herniated disc, also known as a ruptured disc, occurs when the gel-like interior of an intervertebral disc protrudes through the weakened outer layer. This can cause pain and muscle weakness in the body regions supplied by the affected spinal nerve.
Step-by-step explanation:
A herniated disc, also known as a ruptured disc, occurs when the nucleus pulposus, the gel-like interior of an intervertebral disc, protrudes through the weakened or damaged outer layer called the anulus fibrosus. This can happen when bending forward and lifting a heavy object. The pressure exerted on the disc causes the nucleus pulposus to push against a spinal nerve, resulting in pain and/or muscle weakness in the body regions supplied by that nerve. The most common sites for disc herniation are the L4/L5 or L5/S1 intervertebral discs, which can cause sciatica, a radiating pain from the lower back down the thigh and into the leg. Similarly, injuries of the C5/C6 or C6/C7 intervertebral discs can produce pain in the neck, shoulder, and upper limb.