Articular process

Bony projections on vertebrae that form joints

Articular Process

The articular processes are projections of the vertebrae that serve as points of articulation with adjacent vertebrae. These processes are critical components of the vertebral column, contributing to the spine's flexibility and stability.

Articular processes of a vertebra, shown in a lateral view.

Anatomy

Each vertebra typically has two pairs of articular processes: the superior articular processes and the inferior articular processes. These processes arise from the junctions of the pedicles and laminae of the vertebrae.

Superior Articular Processes

The superior articular processes project upward from a vertebra and articulate with the inferior articular processes of the vertebra above. The articular surfaces of these processes are usually oriented in a way that allows for a range of motion while maintaining stability.

Inferior Articular Processes

The inferior articular processes project downward and articulate with the superior articular processes of the vertebra below. The orientation of these processes varies along the spine, adapting to the specific range of motion required in different regions.

Function

The primary function of the articular processes is to form the zygapophysial joints, also known as facet joints, which are synovial joints that allow for movement between the vertebrae. These joints are crucial for the flexibility of the spine, enabling movements such as flexion, extension, lateral flexion, and rotation.

Articular processes shown in a superior view of a vertebra.

Regional Variations

The orientation and size of the articular processes vary along the vertebral column, reflecting the different functional demands of each region.

Cervical Region

In the cervical vertebrae, the articular processes are oriented in a more horizontal plane, allowing for a greater range of motion, particularly rotation. This is essential for the mobility of the neck.

Cervical vertebra showing articular processes.

Thoracic Region

In the thoracic vertebrae, the articular processes are oriented in a more coronal plane, which limits flexion and extension but allows for some rotation. This orientation helps stabilize the thoracic spine, which is also supported by the rib cage.

Lumbar Region

In the lumbar vertebrae, the articular processes are oriented in a more sagittal plane, which facilitates flexion and extension but restricts rotation. This orientation supports the weight-bearing function of the lumbar spine.

Clinical Significance

The articular processes and the facet joints they form are common sites of osteoarthritis and other degenerative changes, which can lead to back pain and reduced mobility. Conditions such as facet joint syndrome and spondylolisthesis often involve the articular processes.

Articular processes in relation to the vertebral foramen.

Related Pages

• Vertebral column
• Zygapophysial joint
• Spinal cord
• Intervertebral disc