Discuss the structure, relationships, innervation (sensory and motor), vasculature, and lymphatics of the intervertebral disc.

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Structure – The chief union b/n adjacent vertebral bodies is secured by the intervertebral discs. They allow movements b/n the vertebra, and serve as a shock absorber. The IVD is a symphysis b/n vertebral bodies. It is sandwiched b/n the plates of hyaline cartilage that cover the superior and inferior surfaces of adjacent vertebral bodies. Each disc is named/numbered according to the vertebra above it. There is no disc b/n the axis and atlas. The 1st IVD is b/n C2 and C3. The IVD conforms in shape to the apposing surfaces of the vertebral bodies b/n which it lies. The discs account for ¼ of the height of the vertebral column. The discs are thinnest in the lumbar region, and thinner anteriorly than posteriorly. IVDs are very tough, and well-suited for resisting displacement of the vertebra on one another, all while allowing some mvt. An IVD consists of a tough, peripheral fibrocartilaginous ring called the annulus fibrosis and a more pliable, inner, gelatinous mass – the nucleus pulposis. The annulus is composed of dense collagen fibers in the outer and fibrocartilage in the more central, part of the ring. These fibers are anchored in the hyaline cartilage covering the bone surfaces, secured by calcification of the cartilage. When the nucleus pulposus is compressed, it changes its shape and distends the annulus by slightly altering the angle b/n the collagen fiber bundles. The nucleus pulposis is white, glistening, and made of a semisolid matrix with some collagen fibers (although not in a specific orientation). It has the capacity to absorb water, accounting for the gain in height over night. The percentage of water in the nucleus pulposis decreases with age. Support is largely due to the anterior and posterior longitudinal ligaments (prevent herniation)

R/ships – anterior = anterior longitudinal ligament, posterior = posterior longitudinal ligament, superior = inferior surface of the body of superior vertebra, inferior = superior surface of the body of inferior vertebra, lateral = anterior longitudinal ligament (anteriorly), sympathetic trunk, psoas major muscle

Innervation – Recurrent meningeal branches (are given off by each spinal nerve as soon as it is formed in the intervertebral foramen, reenters vertebral canal with sensory as well as sympathetic efferent fibers, each nerve divides into ascending and descending branches and supplies the periosteum, the posterior longitudinal ligament, and the outer lamina of the annulus fibrosis over at least 2 adjacent vertebra) – sinuvertebral nerves. Nerve fibers do NOT penetrate the deeper layers of the annulus fibrosis or the nucleus pulposis

Vasculature – IVDs are avascular except for their peripheries, which are supplied from adjacent blood vessels.

Lymphatics – lumbar nodes (?)

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-- LorenEvey - 27 Sep 2006
Topic revision: r1 - 27 Sep 2006, UnknownUser
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