1. Review the bony landmarks.
Back vertebrae, meninges, and spinal cord. Review the bony landmarks: spinous process, transverse process, lamina, superior articular processes, inferior articular processes, body of the vertebra, pedicle, dorsum of the sacrum, sacral hiatus. The seven cervical vertebrae are unique to the rest of the vertebrae in the column. Note that the spinous processes of the cervical vertebrae are bifid. The distinguishing feature is the foramina within the processes, called transverse foramina. Transverse foramina house the vertebral arteries. There are three atypical cervical vertebrae. The first, C7, known as the spina prominens is characterized by its noticeably longer spinous process. Due to its structure, C7 is the one of the most frequently injured. This vertebra can be palpated clinically by moving your hand inferiorly along the neck until you feel a prominent protrusion along the vertebral column. C1 is also known as the atlas because it is fused with the bottom of the skull and bears its weight. C1 has neither a spinous process, nor a body. C2, or the axis, allows the skull to rotate in relation to the spinal column. C2 is characterized by the odontoid process, or the dens, that serves to pivot for the atlas. There are twelve thoracic vertebrae. They are most easily identified by their size and presence of costal facets for articulation with the ribs. Their spinous processes are long and slender and project inferiorly. The five lumbar vertebrae bear most of the body weight. For this reason, they have the largest bodies of all the vertebrae. Lumbar vertebrae lack costal facets and have short, thick spinous processes. The spaces above or below L4 are common sites for lumbar spinal puncture, or spinal tap. A spinal tap may be performed for the administration of anesthesia or to obtain a sample of cerebrospinal fluid. Usually the spinal cord ends at the level of L2 or L3 and therefore a physician can safely aspirate fluid at the level of L4 without damaging the spinal cord. In order to identify the level of L4 clinically, recall that it is located in the same transverse plane as the superior border of the iliac crest. The five vertebrae of the sacrum are fused into a single plate-like structure. The coccyx, or tailbone, usually consists of four small fused vertebrae. These vertebrae lack any resemblance to the vertebrae above them and form a small triangular structure.