Final answer:
Flexion in the sagittal plane decreases the angle of a joint, while extension increases it. The movements of the vertebral column involve the symphysis joint and the plane type of synovial joint.
Step-by-step explanation:
Flexion and Extension
Flexion and extension are movements that take place within the sagittal plane and involve anterior or posterior movements of the body or limbs. For the vertebral column,
flexion (anterior flexion) is an anterior (forward) bending of the neck or body, while extension involves a posterior-directed motion, such as straightening from a flexed position or bending backward.
Lateral flexion is the bending of the neck or body toward the right or left side. These movements of the vertebral column involve both the symphysis joint formed by each intervertebral disc, as well as the plane type of synovial joint formed between the inferior articular processes of one vertebra and the superior articular processes of the next lower vertebra.