Blood Cells

White cells, Red cells and Platelets are made in the bone marrow - a jellylike substance that fills the cavities of bones. Bone marrow consists of fat, blood and special cells (stem cells) that turn into the various kinds of blood cells.

Blood cells in babies and very young children are made in the bone marrow of most of the bones in the body. As we get older, some of the bone marrow converts to yellow marrow and just the bones that make up the spine (vertebrae), ribs, pelvis, skull and sternum contain red marrow.