The medulla spinalis could be a long, thin, hollow structure created of animal tissue, that extends from the medulla within the brain stem to the body part region of the spine. It encloses the central canal of the medulla spinalis, that contains humour. The brain and medulla spinalis along compose the central systema nervosum (CNS). In humans, the medulla spinalis begins at the membrane bone, passing through the hiatus and getting into the vertebral canal at the start of the cervical vertebrae. The medulla spinalis extends right down to between the primary and second body part vertebrae, wherever it ends. The insertion bony spine protects the comparatively shorter medulla spinalis. it's around forty five cm (18 in) in men and around forty three cm (17 in) long in girls.