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 – a spongy material in the middle of our bones. Stem cells stay in the marrow until they have matured into red blood cells, platelets or white blood cells. They are then released into your blood. The levels of these cells in your blood are measured in a blood test called a full blood count (FBC).

Lymphocytes are a type of white blood cell. They travel round the body in the blood and in the lymphatic system, which is part of the body’s immune system. The lymphatic system is made up of lymphocytes, the bone marrow, thymus, spleen, and lymph nodes. It helps to protect us from infection and disease and it drains fluid from the body’s tissues.

The lymph nodes throughout your body are connected by a network of fine tubes (lymphatic vessels). Lymph nodes filter disease and germs. If you have an infection, lymph nodes nearby often swell while they fight it.

The blood

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

Blood is made up of blood cells, which float in a liquid called plasma. Blood cells are made in the bone marrow. This is a spongy material that’s found in the middle of our bones, particularly in our pelvis and backbone (spine). 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 cells called lymphocytes
  • myeloid stem cells, which make all the other types of blood cells: 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, immature, blood cells are called blast cells. They don’t look like mature cells and they can’t do the jobs that mature cells do. Usually, blast cells stay in the bone marrow until they have matured into red blood cells, platelets or white blood cells.

Blood cells
Blood cells

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The mature 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 blood to 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.

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
Red blood cells (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 what levels they use. They 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 ALL soon get used to these figures and what they mean. But remember, you can always ask your medical team for further explanation if you need it.

Lymphocytes

Lymphocytes are a type of white blood cell. There are two main types, B-lymphocytes and T-lymphocytes (also called B-cells and T-cells). Lymphocytes travel round the body in the blood and in the lymphatic system.


The lymphatic system

The lymphatic system is part of the immune system. It helps to protect us from infection and disease and it drains fluid from the body’s tissues.

It’s made up of lymphocytes and organs such as the bone marrow, thymus, spleen, and lymph nodes.

There are lymph nodes throughout the body connected by a network of fine tubes called lymphatic vessels. The lymph nodes filter disease and germs (bacteria and viruses) from lymph, a liquid that travels through the lymphatic vessels. If you have an infection, for example a sore throat, lymph nodes close by often swell while they fight it.

There are lymph nodes in the neck, armpits and groin. Doctors can feel them when they examine these parts of the body. There are also lymph nodes in the chest and the tummy (abdomen).

Lymphatic system
Lymphatic system

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