Bone Marrow
Bone marrow, the soft, pulpy tissue that fills bone cavities, contains a network of blood vessels and fibers surrounded by fat and blood-producing cells. In children, the cells that give rise to blood cells can be found throughout the marrow. In adults, these cells are found mostly in the red marrow of the bones of the chest, hips, back, skull, and of the upper arms and legs. The marrow in the long shafts of bones gradually loses its ability to manufacture blood . This marrow, which is dominated by fat cells and takes on a yellowish color, is called yellow marrow. This cross section of a long bone shows yellow bone marrow in the shaft of a long bone. Red marrow consists primarily of a loose, soft network of blood vessels and protein fibers interspersed with developing blood cells. The blood vessels are termed the vascular component, and the protein fibers and developing blood cells collectively are referred to as the stroma, or the extravascular component. The protein fibers crisscros