Chapter 9

At the conclusion of this chapter, the student should be able to:

• 1. Name, locate, and describe the structures and ligamentous reinforcements of the articulations of the spinal column and thorax.
• 2. Name and demonstrate the movements possible in joints of the spinal column and thorax, regardless of starting position.
• 3. Name and locate the muscles and muscle groups of the spinal column and thorax and name their primary actions as agonists, stabilizers, neutralizers, or antagonists.
• 4. Analyze the fundamental movements of the spinal column and thorax with respect to joint and muscle actions.
• 5. Describe the common injuries of the spinal column and thorax.
• 6. Perform an anatomical analysis of the movements of the spinal column in a motor skill.

If you were faced with the problem of devising a single mechanism that would simultaneously (1) give stability to a collapsible cylinder, (2) permit movement in all directions and yet always return to the fundamental starting position, (3) support three structures of considerable weight (a globe, a yoke, and a cage), (4) provide attachment for numerous flexible bands and elastic cords, (5) transmit a gradually increasing weight to a rigid basinlike foundation, (6) act as a shock absorber for cushioning jolts and jars, and (7) encase and protect a cord of extreme delicacy, you would be staggered by the immensity of the task. Yet the spinal column fulfills all these requirements with amazing efficiency. It is at the same time an organ of stability and mobility, of support and protection, and of resistance and adaptation. It is an instrument of great precision, yet of robust structure. Its architecture and the manner in which it performs its many functions are worthy of careful study. From the kinesiological point of view, we are interested in the spine chiefly as a mechanism for maintaining erect posture and for permitting movement of the head, neck, and trunk.

To understand these functions of the spine, it is necessary to have a clear picture, first, of the spinal column as a whole and, second, of the distinguishing characteristics of the different regions. The spinal column, consisting of seven cervical, twelve thoracic, and five lumbar vertebrae, the sacrum (five fused sacral vertebrae), and the coccyx (three to five fused vertebrae), presents four curves as seen from the side (Figure 9.1). At birth, the vertebral column is convex backward. The thoracic and sacrococcygeal curves remain convex to the rear and are considered primary curves. The cervical and lumbar curves reverse direction of the curvature during infancy and early childhood and are referred to as secondary curves. The curvature at the cervical region develops when the infant raises its head; the lumbar region develops its anterior convexity when the infant assumes an upright posture and begins to walk. The curves are a response to gravity and continue to develop through puberty.

###### Figure 9.1

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