Leukaemia, blood cells and bone marrow
To help you understand leukaemia it can help to know a little about the blood and bone marrow.
Leukaemia is a cancer of the white blood cells. Knowing a bit about how blood cells are made in the body can help you to understand leukaemia and how it’s treated. It might help to watch this short animation on .
All blood cells are made in the bone marrow, which is like a blood cell factory inside our bones. A special type of cell in the bone marrow, called a stem cell, can make any kind of blood cell your body needs.
There are three main types of blood cells:
- White blood cells – which help us fight infection.
- Red blood cells – which carry oxygen from the lungs around our body.
- Platelets – which clot our blood to stop us bleeding when we cut ourselves.
The bone marrow normally makes millions of blood cells every day. To begin with, these new blood cells, called blasts, are not fully developed (they’re immature).
The main job of blast cells is to make more blood cells like themselves. They can’t do any of the jobs that mature blood cells can do, like carrying oxygen or fighting infection. Blast cells normally stay inside the bone marrow until they’ve matured into fully-developed blood cells.
Once blood cells are mature they‘re ready to do their jobs. They leave the bone marrow and go into the bloodstream, where they can be carried to wherever they’re needed.
In leukaemia, the process for making new white blood cells gets out of control and immature white blood cells (blasts) keep being made.
They build up in the bone marrow until there isn’t enough room for the bone marrow to make healthy white cells, red cells and platelets.
Leukaemia is a cancer of the white blood cells. Healthy white blood cells are made from two types of blood cells:
- lymphoblasts that make lymphocytes
- myeloid cells (myeloblasts) that make other types of white blood cells such as neutrophils.
Leukaemias are named after the type of white blood cell that has become abnormal and started growing out of control. The most common types in teenagers and young adults are AML and ALL:
- Leukaemia that starts from abnormal myeloid cells is called acute myeloid leukaemia - or AML for short.
- Leukaemia that starts from abnormal lymphoblasts is called acute lymphoblastic leukaemia (ALL).
There are other types of leukaemia that are more common in older people. You can find out more in our general leukaemia section for people of all ages.
The information in this section is about ALL, but if you have a different type of leukaemia and want to know more, please contact us.
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If you're looking for information about ALL in people of all ages, please see our general ALL section.