Bone Marrow Basics
Bone marrow is soft, spongy tissue found inside the bone. All blood starts out as stem cells, “parent cells” produced in the bone marrow. Stem cells develop into one of the three types of mature blood cells – red blood cells, white blood cells, and platelets – and enter the bloodstream. Red blood cells carry oxygen throughout the body. White blood cells fight infection. Platelets cause blood to clot. The bones of the hip, chest (sternum/breastbone), and pelvis contain the largest amount of marrow and stem cells.
- Stem cells give rise to all blood cells. Each one either divides to form a new stem cell or becomes a mature red blood cell, white blood cell, or platelet.
- White blood cells, also called leukocytes, are the key components of the immune system, the body’s defense against infection, viruses, and other threats. There are many different types of white blood cells, each of which plays a specific role in destroying “foreign” substances.
- Red blood cells, also called erythrocytes, contain hemoglobin, a protein that carries oxygen from the lungs to the rest of the cells in the body.
- Platelets are sticky, disc-shaped cells that enable blood to clot properly, which prevents excess bleeding.
Some stem cells also circulate in the bloodstream. These are called peripheral blood stem cells (PBSCs). Improved methods for collecting and storing peripheral blood stem cells have made this an increasingly important source of stem cells for certain types of transplants (especially for autologous bone marrow/stem cell transplantation).