The blood and the lymphatic system

Blood is made up of blood cells and a liquid called plasma. Blood cells are made from blood stem cells in the bone marrow – this is a spongy material in the middle of our bones. Millions of new blood cells are made every day.

Blood stem cells are divided into two types:

  • Lymphoid stem cells make lymphocytes, a type of white blood cell.
  • Myeloid stem cells make red blood cells, other types of white blood cells and platelets.

Once the cells have matured, they are released into your blood. They all have different roles.

  • Red blood cells carry oxygen around the body.
  • Platelets help your blood clot.
  • White blood cellsfight and prevent infection.

A blood test called a full blood count (FBC) measures the levels of these cells in your blood. Your doctors and nurses can explain these to you and what the numbers mean. At first you may find the numbers confusing but most people with AML soon get used them.

The blood

To help you understand AML and its treatment, it is useful to know a bit about your blood, how it’s made and what it does.

Blood is made up of blood cells, which move around in a liquid called plasma. Blood cells are made in the bone marrow. This is a spongy material in the middle of our bones – particularly in our pelvis, backbone (spine) and breast bone (sternum). Normally, millions of new blood cells are made every day to replace old and worn-out blood cells.

All blood cells are made from cells called blood stem cells.

There are two types of blood stem cell:

  • lymphoid stem cells, which make a type of white blood cell called lymphocytes
  • myeloid stem cells, which make all the other types of blood cell: red blood cells, platelets, and white blood cells.

Blood stem cells in the bone marrow divide and grow to make new blood cells. The new, developing blood cells are called blast cells. They don’t look like fully developed cells and they can’t do the jobs that fully developed cells do. Usually, blast cells stay in the bone marrow until they have developed into red blood cells, platelets or white blood cells.

Blood cells
Blood cells

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The developed cells are then released into your blood to carry out different functions:

  • Red blood cells contain haemoglobin (Hb), which carries oxygen from your lungs to all the cells in your body.
  • Platelets are very small cells that help your blood clot and prevent bleeding and bruising.
  • White blood cells fight and prevent infection. There are several types of white blood cell. The two most important types are neutrophils and lymphocytes. Neutrophils are a type of granulocyte.

The levels of these cells in your blood are measured in a blood test called a full blood count (FBC). The figures below are a guide to the levels usually found in a healthy person.

Type of blood cellLevels found in a healthy person
Haemoglobin (Hb)130–180g/l (men)
115–165g/l (women)
Platelets150–400 x 109/l
White blood cells (WBC)4.0–11.0 x 109/l
Neutrophils2.0–7.5 x 109/l
Lymphocytes1.5–4.5 x 109/l

These figures can vary from hospital to hospital. Your doctor or nurse will be able to tell you which levels they use. The levels can also vary slightly between people from different ethnic groups.

The figures might look complicated when they’re written down, but in practice they’re used in a straightforward way. For example, you’ll hear doctors or nurses saying things like, ‘Your haemoglobin is 140,’ or, ‘Your neutrophils are 4’.

Most people with AML soon get used to these figures and what they mean. But remember, you can always ask your medical team to explain more if you need to.

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