Which of the following structures are best demonstrated on the lateral projection of the thoracic spine?

The best demonstration of structures in the lateral projection of the thoracic spine is the zygapophyseal joints. This projection allows for a clear view of these facet joints, which are located between adjacent vertebrae and provide critical insights into spinal alignment and potential joint issues.

In a lateral view, the zygapophyseal joints are positioned in such a way that they can be visualized in profile, making it easier to assess their condition. The lateral projection also facilitates the evaluation of relationship between the vertebrae, which is essential for diagnosing various spinal disorders.

Other structures, like intervertebral foramina, are best demonstrated in an oblique view rather than laterally. This lateral projection does not provide a comprehensive view of transverse processes or laminae, as they may be obscured depending on the angle of the X-ray beam and patient positioning. Thus, for assessing the thoracic spine, the lateral projection is particularly advantageous for evaluating the zygapophyseal joints.