The ring of fibrocartilage and fibrous tissue forming the circumference of the intervertebral disc; surrounds the nucleus pulposus, which is prone to herniation when the annulus fibrosus is compromised. [ http://purl.obolibrary.org/obo/BTO_0003629 http://en.wikipedia.org/wiki/Annulus_fibrosus_disci_intervertebralis ]