Chapter 4 The Skeletal System 137 • The superior and inferior articular processes are indentations or facets where a vertebra articulates, or joins, with the vertebrae immediately above and below. These articulations are called facet (FAS-eht) joints. Vertebral size increases progressively from the cervical region down through the lumbar region (Figure 4.14). This gradual size increase serves a functional purpose. When the body is in an upright position, each vertebra must support the weight of all of the body parts positioned above it. Think about what this means. While a cervical vertebra supports only the weight of the head and neck, a lumbar vertebra supports the weight of the head, neck, arms, and all of the trunk positioned above that vertebra. The size and angulation of the vertebral processes also vary throughout the spinal column. This changes the orientation of the facet joints, which connect the vertebrae and limit range of motion in the different spinal regions. The Spinal Curves The characteristic shapes of the vertebrae in the different spinal regions also form the normal spinal curves. As Figure 4.11 shows, the cervical and lumbar curves are posteriorly concave, while the thoracic, sacral, and coccyx curvatures are anteriorly concave. These alternating curves make the spine stronger and better able to resist potentially injurious forces than if it were straight. The thoracic and sacral curves are known as primary spinal curves because they are present at birth. The lumbar and cervical curves are referred to as secondary spinal curves. They develop after the baby begins to raise the head, sit, and stand, as increased muscular strength enables the young child to shift body weight to the spine. Abnormal spinal curvatures can develop due to genetic or congenital abnormalities or when the spine is habitually subjected to asymmetrical forces (Figure 4.15). Exaggeration of the lumbar curve is termed lordosis (lor-DOH-sis), accentuation of the thoracic curve is called kyphosis (kigh-FOH- sis), and any lateral deviation of the spine is known as scoliosis (skoh-lee-OH-sis). © Body Scientific International Figure 4.13 Three views of a typical vertebra. What are the names of the indentations on the articular processes? Vertebral arch Articular processes Superior articular process Superior articular process Inferior articular facet Inferior articular facet Transverse process Transverse process The major components of a typical vertebra (superior view) Lateral and slightly inferior view Inferior view Vertebral body Vertebral body Spinous process Spinous process Inferior articular process Pedicle Pedicle Arrow passing through vertebral foramen Vertebral body Vertebral foramen Copyright Goodheart-Willcox Co., Inc.