The structure and function of the intervertebral disc 1, structure of the normal human intervertebral disc a total of twenty-three (the 1st, 2 cervical intervertebral no disc), located between two adjacent vertebrae, keeping the vertebrae separated from each other, to avoid friction and collision between bone and bone. The intervertebral disc consists of 3 parts: the fibrous ring, the cartilage plate, and the nucleus pulposus, and is a flexible cushion that accounts for about one-fourth of the full length of the spine during the filling period. (1) cartilage plate: composed of glass-yang transparent cartilage, one on and one below the vertebral body, forming the upper and lower part of the intervertebral disc, closely connected with the vertebral body. During the juvenile period, the cartilage plate is thick, and when the circumferential epiphyseal ring is completely ossified and fused with the vertebral body, the cartilage plate becomes thinner and sunken into the epiphyseal ring. The edge of the cartilage plate is fixed with fibers above the epiphyseal ring. (2) Fibrous rings: tough fibrocartilaginous tissue, arranged in a centripetal hierarchy. The fibers of each layer are arranged at an angle of 30 to 60 degrees and are connected obliquely to the adjacent upper and lower vertebral body edges in a lattice pattern. The nucleus pulposus is held centrally due to the encirclement of the fibrous ring. The periphery of the fibrous ring is not only closely connected with the upper and lower epiphyseal rings, but also heals with the anterior and posterior longitudinal ligaments. (3) Nucleus pulposus: The nucleus pulposus is composed of elastic and soft pulpy grayish-white semi-solid material, located in the center of cartilage plate and fibers. The nucleus pulposus itself has great tension and no certain shape, and can be deformed with the movement of the spine. In the early stage, the water content of the nucleus pulposus is about 80 percent, but as it ages, its water content gradually decreases, and in adults there is no obvious demarcation between the nucleus pulposus and the fibrous ring, and in old age the intervertebral disc becomes a mass like a porridge. Due to the atrophy of the intervertebral disc, the lordosis of the thoracic spine increases significantly, forming a hunchback, shortening the length of the spine and making the body significantly shorter. There is a common pattern in the growth and development of intervertebral discs. It can be divided into three stages according to age: 1 to 20 years old for growth and development; 20 to 30 years old for development and maturation; and after 30 years old for degeneration. Fully mature intervertebral discs have thin cartilage plates embedded in the upper and lower epiphyseal rings of the vertebral body; the tension of the fibrous ring is large and elastic. The intervertebral discs exchange fluid with the vertebral body by means of the permeability of the cartilage plate to maintain its metabolism. 2, function (1) connect the spine, generate movement: the vertebrae of the spine are connected to each other by intervertebral discs. Its movement is related to the function of the intervertebral discs. In the various movements of the spine, the intervertebral discs are not only deformed, but also protrude in the opposite direction of the movement. Due to the presence of intervertebral discs, the spine has a variety of motion functions such as forward flexion, backward extension, lateral bending, and rotation. (2) Weight-bearing: When weight-bearing, the disc relies on the elasticity of the nucleus pulposus, the tension of the annulus fibrosus, and the deformation of the cartilage plate to adapt. When these tissues are sound, they can withstand considerable pressure without damage. As determined by human testing, when lying flat in a state of muscle relaxation, the lumbar nucleus pulposus pressure is approximately twelve kilograms or slightly higher. In the upright position, the pressure is twelve kilograms plus the sum of its weight above the plane, that is, about forty-five to sixty kilograms. When the spine is in motion, the nucleus pulposus can act as a fulcrum for leverage, and the pressure is higher; when the spine is naturally extended from forward flexion, the pressure can increase by 30 to 50 percent. When doing strenuous activities or lifting heavy objects, the pressure can increase to hundreds of kilograms over time. The cadaveric spinal disc measurement proved that the normal pulpal nucleus can withstand a pressure of three hundred kilograms without rupture, that is, about sixty kilograms of weight per square centimeter. The effect of these gravitational forces is mainly the vertical pressure from top to bottom, so that the disc tissue to the surrounding expansion (spread), when the pressure is lifted, due to its own elasticity and tension and recovery. (3) shock absorption, protection of the central nerve: due to the existence of the intervertebral disc, to avoid direct friction and impact between the vertebrae, people in daily activities, labor or life, constantly from the outside into the body of vibration, impact on the spine, the intervertebral disc is like a spring and rubber cushion to play a cushioning external shock absorption, protection of the central nerve role, without causing damage to the body.