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# Chapter Eight: Skeletal System: Axial and Appendicular Skeleton ## 8.5 Bones of the Vertebral Column The adult vertebral column is composed of 26 bones, including 24 individual vertebrae and the fused vertebrae that form both the sacrum and the coccyx. Each vertebra (except the first and the...

# Chapter Eight: Skeletal System: Axial and Appendicular Skeleton ## 8.5 Bones of the Vertebral Column The adult vertebral column is composed of 26 bones, including 24 individual vertebrae and the fused vertebrae that form both the sacrum and the coccyx. Each vertebra (except the first and the last) articulates with one superior vertebra and one inferior vertebra. **Consider the vertebral column's general function and regions, the curves of the spine.** ### 8.5a Types of Vertebrae The vertebral column provides vertical support for the body and supports the weight of the head. It helps maintain an upright body position. Most important, it houses and protects the delicate spinal cord. **Five Divisions of the Vertebral Column:** - **Seven cervical vertebrae** (designated C1-C7) form the bones of the neck (cervical region). The first cervical vertebra (C1) articulates superiorly with the occipital condyles of the skull. The seventh cervical vertebra articulates inferiorly with the first thoracic vertebra - **Twelve thoracic vertebrae** (designated T1-T12) form the superior region of the back (thoracic region). Each thoracic vertebra articulates laterally with one or two pairs of ribs. The twelfth thoracic vertebra articulates inferiorly with the first lumbar vertebra. - **Five lumbar vertebrae** (designated L1-L5) form the inferior concave region of the back (lumbar region). The fifth lumbar vertebra articulates inferiorly with the first sacral vertebra. - **The sacrum** is formed from five sacral vertebrae (designated S1-S5) that fuse into a single bony structure by the mid-to-late 20s. The sacrum articulates with L5 superiorly, the first coccygeal vertebra inferiorly, and laterally with the coxae (hip bones). - **The coccyx** is commonly called the tailbone and is formed from four coccygeal vertebrae (designated Co-Co4) that start to unite during puberty and is complete by the mid-20s. The first coccygeal vertebra may fuse to the sacrum. ### 8.5b Spinal Curvatures The vertebral column has four spinal curvatures and is rigid. When viewed from the side, it has four spinal curves, the cervical and lumbar curvatures. These curves are apparent when the body is standing.