Blood and bone marrow

To understand blood cancers, it can help to know more about your blood and blood cells.

To understand blood cancers, it can help to know more about your blood and blood cells.

Blood is made up of different types of blood cells, which float in a liquid called plasma. Blood cells are made in the bone marrow. This is the spongy material found inside bones.

Most blood cells are made in the:

  • back of the hips (pelvis)
  • backbone (spine)
  • breast bone (sternum).

The bone marrow usually makes billions of new blood cells every day. These new cells replace old and worn-out blood cells.

Blood cells start from stem cells. These are blood cells at the earliest stage of their development. Stem cells divide to make one of the following types of cell:

  • Lymphoid stem cells, which make a type of white blood cell called lymphocytes.
  • Myeloid stem cells, which make other white blood cells, such as neutrophils and red blood cells and platelets.
This diagram shows how all blood cells are made from stem cells. At the top of the diagram, is a stem cell. It has two arrows pointing downwards. One points to a lymphoid stem cell and one points to a myeloid stem cell. The lymphoid stem cell has two arrows pointing to the blood cells it makes. These are a B-cell lymphocyte and a T-cell lymphocyte. These lymphocytes are both types of white blood cells. The myeloid stem cell has three arrows pointing to the blood cells it makes. These are a red blood cell, a platelet and a neutrophil. A neutrophil is a type of white blood cell. 

Blood cells go through different stages of development before they are ready to leave the bone marrow. All blood stem cells develop into immature cells (called blast cells). They then develop into mature, red blood cells, platelets or white blood cells. Once this happens, they go into your blood and do different things:

  • Red blood cells carry oxygen from your lungs to all the cells in your body.
  • White blood cells fight and prevent infection. There are different types of white blood cell. The most important ones are neutrophils and lymphocytes.
  • Platelets help your blood to clot and prevent bleeding and bruising.

The levels of these cells in your blood are measured in a test called a full blood count (FBC). The table below gives an idea of the normal ranges for certain blood cells in a healthy adult. The normal range in different laboratories can be slightly different.

 Type of cell  Levels found in a healthy person
 Red blood cells – measured in haemoglobin (Hb) levels 130-180g/l (men)
115-165g/l (women)
 Platelets 150-400 x 109/l 
 White blood cells (WBC) 4.0-11.0 x 109/l 
 Neutrophils 2.0-7.5 x 109/l 
 Lymphocytes 1.5-4.5 x 109/l