136 Introduction to Anatomy & Physiology Structures of the Vertebrae Although no two vertebrae are exactly alike, most of the vertebrae have several structural features in common (Figure 4.13): • The vertebral body is the thick, disc-shaped portion that bears weight and forms the anterior portion of the vertebra. • The vertebral arch is the round projection of bone on the posterior aspect of the vertebra. It surrounds a hole known as the vertebral foramen (foh-RAY-mehn), through which the spinal cord passes. • The transverse processes are bony projections on the lateral sides of the vertebral arch. In anatomy, a process is a projection on a bone or other tissue. • The spinous process is a bony projection that extends posteriorly. 3. The lumbar (LUM-bar) region includes the five vertebrae found in the lower back. 4. The sacrum (SAY-krum) consists of five fused vertebrae that form the posterior portion of the pelvic girdle. 5. The coccyx (KAHK-siks), or tailbone, located at the bottom of the spine, includes four fused vertebrae. © Body Scientific International Figure 4.11 The vertebral column (spine). How many bones make up the sacrum? The coccyx? How do these bones differ from the bones of the other three regions of the vertebral column? Cervical region C5 C6 C7 T1 T2 T3 T5 T4 L1 L2 L3 L5 L4 T6 T7 T8 T9 T10 T11 T12 C1 C2 C3 C4 Thoracic region Lumbar region Sacrum Cervical curve Thoracic curve Lumbar curve Sacral curve Coccyx © Body Scientific International Figure 4.12 The first and second cervical vertebrae, the atlas and the axis. Posterior arch Superior articular facet Superior articular facet Odontoid process Body Spinous process Pedicle Posterior tubercle Atlas Axis Copyright Goodheart-Willcox Co., Inc.