Your blood and circulation are very important for your day-to-day health as the body’s main transport system.
Your blood circulation is a network of arteries, veins and capillaries carrying blood to every part of the body. You have around five litres of blood circulating in your body (1).
The blood carries the oxygen you breathe in through the lungs to the body’s cells. It picks up carbon dioxide carrying it back to the lungs, where you breathe it out (1).
Blood also carries nutrients to the cells and carries waste products from the cells to the kidneys and liver to be processed and removed from the body (1).
There are billions of cells in your blood. They are constantly being used up and need to be replaced. Every day, on average, you make around 200 billion red cells, 10 billion white cells and 400 billion platelets (2).
Most blood cells are made in the bone marrow – all your red cells and platelets and about two-thirds of your white cells. The remaining white cells start off in the bone marrow but finish developing in the organs of the lymphatic system, the spleen, lymph nodes and thymus (2).
Neutrophils are the most numerous type of white blood cell. They are extremely important in fighting infection (4). If you’re having chemotherapy, you may be told that you are ‘neutropenic’. That means that your neutrophil count is very low and you are at risk of picking up infections (5).
Find out more: What are blood stem cells?
1. Blood basics. American Society of Haematology. Accessed July 2021.
2. Blood cell formation. Encyclopaedia Britannica. Accessed July 2021.
3. Blood cells. Blood Cancer UK. Accessed July 2021.
4. Neutrophil. Encyclopaedia Britiannica. Accessed July 2021.
5. Neutropenia. Lymphoma Action. Last reviewed July 2018.