Dalley, 10th Edition

97

Vertebral Column

VERTEBRAL COLUMN

Intervertebral (IV) discs provide strong attachments between the vertebral bodies, uniting them into a continu ous semirigid column and forming the inferior half of the anterior border of the IV foramen. In aggregate, the discs account for 20–25% of the length (height) of the vertebral column (see Fig. 2.2). As well as permitting movement be tween adjacent vertebrae, their resilient deformability allows

The vertebral column (spine) is an aggregate structure, normally made up of 33 vertebrae and the components that unite them into a single structural, functional entity—the “axis” of the axial skeleton (see Fig. 2.2). Because it provides the semirigid, central “core” about which movements of the trunk occur, “soft” or hollow structures that run a longitu dinal course are subject to damage or kinking (e.g., the spi nal cord, descending aorta, venae cavae, thoracic duct, and esophagus). Thus, they lie in close proximity to the vertebral axis, where they receive its semirigid support and torsional stresses on them are minimized. Joints of Vertebral Column The joints of the vertebral column include the following: • Joints of the vertebral bodies • Joints of the vertebral arches • Craniovertebral (atlantoaxial and atlantooccipital) joints • Costovertebral joints (see Chapter 4, Thorax) • Sacroiliac joints (see Chapter 6, Pelvis and Perineum) JOINTS OF VERTEBRAL BODIES The joints of the vertebral bodies are symphyses ( second ary cartilaginous joints ) designed for weight bearing and strength. The articulating surfaces of adjacent vertebrae are connected by IV discs and ligaments (Figs. 2.15 and 2.16).

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Superior vertebral notch

Position of exiting spinal nerve within IV foramen of lumbar vertebrae

Superior articular process

Intervertebral (IV) foramen

Intervertebral (IV) disc

Articular capsule of zygapophysial (facet) joint

Anulus fibrosus of IV disc (dissected to show concentric layers)

Ligamentum flavum

Inferior articular process

Lateral view

Inferior vertebral notch

FIGURE 2.16. Lumbar vertebrae and IV discs. Superior lumbar region showing the lamellated structure of the anuli brosi of the discs and the structures involved in formation of IV foramina. Except in the cervical region, the disc forms the inferior half of the anterior boundary of an IV foramen as shown. Thus, herniation of the disc is less likely to affect the spinal nerve that exit from the superior part of that foramen, bounded by bone.

Nucleus pulposus

Posterior longitudinal ligament

Anulus fibrosus

Intervertebral disc

Concentric lamellae (cut)

Anterior longitudinal ligament

Nucleus pulposus

(B) Schematic, dissected isolated disc

Vertebral body

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Anulus fibrosus

Epiphysial rim

Posterior longitudinal ligament

Anterior longitudinal ligament

Cartilage plate

(A) Anterior view

(C) Sagittal section

FIGURE 2.15. Structure of IV discs. A. Portion of dissected lumbar region with sagittal slice shown in C being extracted. B. Intervertebral disc dissected to demonstrate lamellae. C. Sagittal section from A showing eccentric placement of nucleus within disc.