Blood cells grow in the same way as other human cells. They develop in the bone marrow from a parent cell known as a stem cell. Stem cells are immature cells that can develop into all of the different types of blood cells: white blood cells, red blood cells and platelets. Stem cells are usually found inside the bone marrow spaces of large bones. They can also travel from one bone to another by way of the blood stream.
In a blood and marrow transplant, stem cells are harvested, either from the large bones or from the blood stream, and transplanted to the patient. Stem cells collected from the pelvic bone in the lower back are called bone marrow. Stem cells harvested from the blood in the veins are called peripheral blood progenitor cells. This is why blood and marrow transplants are often referred to as blood stem cell transplants. For simplicity, we will use the terms bone marrow and stem cells interchangeably on this site.
Your BMT doctor will discuss how stem cells will be collected from you or your donor.