The Spine: Videos & Practice Problems

The spine, also known as the vertebral column, is a crucial component of the axial skeleton, consisting of 24 vertebrae along with the sacrum and coccyx. The vertebral column is divided into distinct regions, each characterized by specific vertebrae types. The cervical vertebrae, located in the neck, comprise seven vertebrae labeled C1 through C7. The first two cervical vertebrae, C1 (the atlas) and C2 (the axis), are unique; the atlas supports the head, while the axis allows for rotational movement of the head.

Moving down the spine, the thoracic vertebrae, totaling twelve, are found in the chest region and are notable for articulating with the ribs, labeled T1 through T12. Below the thoracic region are the five lumbar vertebrae (L1 through L5), which are the largest and thickest, designed to bear significant weight. The sacrum, a single bone formed from five fused vertebrae, connects the spine to the pelvis, while the coccyx, or tailbone, typically consists of four fused vertebrae.

The spine is not a straight structure; it features four natural curvatures that enhance its strength and flexibility: the cervical curve, thoracic curve, lumbar curve, and sacral curve. These curves allow the spine to absorb shock and provide a spring-like quality, preventing rigidity. Between each vertebra are intervertebral discs made of cartilage and connective tissue, which cushion the vertebrae and allow for limited movement. Notably, intervertebral discs are absent between the atlas and axis, facilitating the unique rotational movement of the head.

The human spine is divided into several regions, each characterized by specific types of vertebrae, a distinct number of bones, and unique curvature patterns. Understanding these components is essential for grasping the overall structure and function of the vertebral column.

The cervical region, located at the top of the spine, consists of seven cervical vertebrae, labeled C1 through C7. This region exhibits a concave curvature when viewed from the side, meaning the concave side faces posteriorly. This curvature is often remembered by visualizing a cave, where the inward curve resembles the entrance to a cave.

Moving down, the coccyx, or tailbone, is represented as a single bone formed from the fusion of 3 to 5 smaller bones. Although the coccyx is not classified as one of the major curves of the spine, it typically presents a convex curvature, with the convex side facing posteriorly.

The lumbar region, which comprises the lower back, contains five lumbar vertebrae, labeled L1 through L5. These vertebrae are larger and more robust, supporting the weight of the upper body. The lumbar curvature is concave, with the concave side again facing posteriorly.

The sacrum, located below the lumbar region, is a single bone formed from five fused sacral vertebrae. It connects the spine to the pelvis and also exhibits a convex curvature, with the convex side facing posteriorly.

Finally, the thoracic region, associated with the chest and rib cage, consists of twelve thoracic vertebrae, labeled T1 through T12. This region has a convex curvature, with the posterior side also facing outward. It is important to note that the curvature of the spine alternates as you move down: cervical (concave), thoracic (convex), lumbar (concave), and sacral (convex). The coccyx does not contribute to this alternating pattern but adds to the overall flexibility and spring-like quality of the spine.

In summary, the vertebral column is a complex structure with distinct regions, each defined by its vertebrae, number of bones, and curvature. This knowledge is crucial for understanding spinal health and anatomy.