What type of forces does the annulus fibrosus in the spinal column help resist?

The annulus fibrosus, which is the outer layer of the intervertebral disc in the spinal column, plays a crucial role in maintaining spinal stability. Its structure is specifically adapted to resist torsional forces. Torsional forces involve twisting or rotational movements that can occur in the spine during various activities, such as lifting or twisting motions.

The annulus fibrosus is composed of a series of collagen fibers arranged in a layered configuration that aligns obliquely to the vertical axis of the spine. This design allows it to effectively handle these twisting forces by providing resistance against deformation during rotation. As the spine undergoes movements, the annulus fibrosus helps to distribute the mechanical loads, thereby protecting the inner nucleus pulposus and maintaining the structural integrity of the disc.

While the annulus fibrosus does have some role in resisting other types of forces, its primary function in the context of the question is to counteract torsional stresses, making it pivotal during movements that involve twisting the spine.