Bone marrow

soft connective tissue found in the cavities of most bones, occuring in two forms: whitish or yellowish marrow ( yellow marrow) consisting chiefly of fat cells and found mainly in long bones: and reddish marrow (red marrow) where most red blood cell and blood granulocyte production occurs; not to be confused with the substance in the spinal canal, which is the spinal cord with totally different structure and function