Bone marrow

Bone marrow is the tissue held within the internal cavities of bone e.g. in adults, the medullary cavity of long bones or the intertrabecullar space in spongy bone. It is divided into:

• red marrow:
  • contains the cellular elements involved in erythropoiesis, thrombopoiesis and granulopoiesis
  • occupies all marrow spaces in pre-pubescents
  • localised to marrow spaces ribs, sternum, vertebrae, shoulder girdle and proximal ends of fermur and tibia in healthy adult
• yellow marrow:
  • contains fat and few quiescent cellular elements
  • displaces red marrow from puberty onwards
  • has the potential to revert back to red marrow at times of stress