The transverse band of the cruciform ligament is a broad strong band of collagen fibers, which form an interlacing mesh in its central part.  The ligament arches behind the dens and attaches to small prominent tubercles on the medial aspect of each lateral mass of C1 (atlas).  Anteriorly, a thin layer of articular cartilage covers the broader central part.  The transverse band divides the ring of C1 into unequal parts; a smaller anterior part containing the dens, which is kept in position when all other ligaments are divided, and a larger posterior part surrounding the spinal cord and its meninges, the anterior and posterior spinal arteries and the spinal root of the accessory nerve (XI cranial nerve).