Reissner's fiber

Reissner's fiber is a fibrous aggregation of secreted molecules extending from the subcommissural organ (SCO) through the ventricular system and central canal to the ampulla caudalis, a small ventricle-like structure at the end of the spinal cord. In vertebrates, Reissner's fiber is formed by secretions of SCO-spondin from the subcommissural organ into the spinal fluid of the ventricular cavity. Reissner's fiber is highly conserved, and present in the central canal of all chordates. In cephalochordates, Reissner's fiber is produced by the ventral infundibular organ, as opposed to the dorsal SCO.