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Vertebrae are classified as irregular bones due to their complex shapes that do not fit into the typical categories of long, flat, or short bones. Irregular bones possess various shapes and structures, allowing them to fulfill specific functions in the body. The vertebrae have a unique structure, with processes and facets for articulation, which aids in the flexibility and movement of the spinal column. This classification is important in understanding the functional role of vertebrae in protecting the spinal cord while allowing for a range of motion and supporting the body’s weight.

Long bones, such as the femur or tibia, are primarily involved in movement and support; flat bones, like the skull and sternum, serve protective functions and are sites for muscle attachment; and short bones, such as those found in the wrist and ankle, provide stability and support with limited movement. These definitions further clarify why vertebrae are not categorized within these other groups, reinforcing their classification as irregular bones.