The outer fibrous layer of an intervertebral disc, which forms a ring around the nucleus pulposus (the gel-like center of the disc). The annulus fibrosus consists of several layers (laminae) of fibrocartilage made up of predominantly type I but also type II collagen. Type I is concentrated toward the edge of the ring, where it provides greater strength. The stiff laminae can withstand compressive forces. The fibrous intervertebral disc contains the nucleus pulposus and this helps to distribute pressure evenly across the disc. This prevents the development of stress concentrations which could cause damage to the underlying vertebrae or to their endplates. The nucleus pulposus contains loose fibers suspended in a mucoprotein gel. The nucleus of the disc acts as a shock absorber, absorbing the impact of the body's activities and keeping the two vertebrae separated.