Blood is your body’s transport, defence and communication system. It helps fight infection, carries nutrients (for energy), and sends messages around your body. Understanding how your blood and bone marrow work can help you understand what blood cancer is, how it affects your body, and how it’s treated.
Your blood is made up of blood cells, which are made in your bone marrow. Each type of blood cell has a particular job to do. If everything’s working normally, your body makes the right number of each type of cell to keep you healthy. If there are too many or too few of any type of blood cell, this can make you unwell.
What is blood for?
Your blood has many jobs:
- Transport – it carries food, oxygen and proteins to different parts of your body. It also carries waste chemicals to your kidneys and lungs so they can get rid of them.
- Defence – white blood cells are part of your immune system, which fights infections. This is the function that's most affected by blood cancer.
- Communication – organs (such as your liver or stomach) release hormones into your blood which send messages to other organs.
- Repair – blood contains cells and chemicals which can seal off damaged blood vessels and control blood loss.
What is blood made of?
Your blood is made up of white blood cells, red blood cells, platelets and plasma.
White blood cells (leukocytes)
These fight and prevent infection. There are five different types of white blood cell, which are lymphocytes, neutrophils, monocytes, eosinophils, and basophils.
There are some white blood cells that it can be helpful to know about when you’re finding out more about blood cancer:
- T cells recognise infected cells and kill them or send instructions to that help your body to fight them. They’re sometimes called T lymphocytes.
- B cells work with T cells to make antibodies that help clump around germs and trap them so other blood cells can come along and get rid of them. They’re sometimes called B lymphocytes.
- Neutrophils are a type of granulocyte that helps the body fight bacterial infections. People with a lower number of neutrophils are more likely to develop bad infections more often and find it harder to fight them.
Red blood cells (erythrocytes)
These contain a protein called haemoglobin, which carries oxygen from your lungs to all the tissues of your body. Your muscles, organs and other tissues need oxygen to produce energy from your food. It's more common to hear doctors talking about the concentration of haemoglobin in the blood than it is to hear them talking about the number of red blood cells.
These stick together at the site of any tissue damage (like a cut) and stop bleeding.
Blood plasma is the liquid part of blood that the blood cells move around in.