Final answer:
The condition involving forward slipping of a vertebra is called spondylolisthesis. The joints between the articular processes of vertebrae allow for flexion, extension, and lateral flexion. Conditions such as herniated discs can arise from vertebral movements, leading to pain and muscle weakness.
Step-by-step explanation:
The unilateral or bilateral results you are referring to lead to a condition known as spondylolisthesis, which involves the forward slipping of an affected vertebra. This can occur due to a variety of causes, including congenital defects, trauma, or degeneration of the spinal joints and ligaments. In terms of movement, the articulation between the articular processes of adjacent vertebrae allows for several types of motion, including flexion and extension, which refer to forward and backward bending motions of the spine. Specifically, when you bend forward, the anterior part of the intervertebral disc is compressed, while its posterior part expands. On the other hand, extension refers to a posterior-directed motion. Other movements enabled by these joints include lateral flexion, which involves bending the spine to the side.
Conditions like herniated discs or sciatica often occur when the disc material protrudes and compresses a spinal nerve, leading to pain and muscle weakness. Herniated discs most often occur at the L4/L5 or L5/S1 levels of the spine. In cases of kyphosis, also known as dowager's hump, vertebrae may become misshapen due to conditions such as osteoporosis, resulting in excessive curvature of the spine.