Fast facts about the spleen1

You probably haven’t heard a lot about your spleen before – it is tucked away under the left top corner of your diaphragm (the muscle that twitches when you hiccup). Your spleen is about 12 centimetres (5 inches) long and is roughly egg-shaped (see figure 1). It is dark red because its job is to filter blood.

Filtering blood and detecting germs in the spleen1

Many white blood cells live in your spleen and do two important jobs there: filtering your blood and detecting germs that could cause infection and disease. Let’s look at these in more detail: • The spleen filters or cleans your blood using macrophages and dendritic cells – types of white blood cell – to consume unwanted materials. The ‘phage’ in macrophage comes from a Greek word that means to eat or devour. These unwanted materials might be all sorts of things, like bacteria, viruses or worn-out red blood cells. Once inside a macrophage or dendritic cell, the waste items are bombarded with chemicals that break them down. • The spleen also helps detect and fight infection. It does this by releasing white blood cells (also called lymphocytes or T cells) which are made in your bone marrow but stored in your spleen. If the white blood cell detects infection, it gets to work by recruiting a team of immune cells. Together, the immune cells track down the infection and destroy it.

How is the spleen structured?1

The cells in your spleen need to come into contact with lots of blood to do their job. The cells and blood are contained in a thin bag of tissue, so your spleen is quite fragile. Your spleen is divided into sections called nodules that each contain an area of red pulp (mainly for filtering) and white pulp, which is where the white blood cells fight infection.

How is the spleen affected by Gaucher disease?2

The spleen may be affected by Gaucher disease, which can cause it to get bigger, stopping it from working properly. Your doctor might use the word splenomegaly to explain your spleen growing in size and causing your tummy to become tender and painful. In a similar way, your liver can also grow bigger (at the same time as the spleen), and you might hear this called hepatosplenomegaly – enlarged spleen and liver.


1. Anatomy and Physiology. OpenStax at Rice University. Published 25 April 2013. ISBN-13: 978-1-947172-04-3. Available at

2. Cappellini MD et al. European Oncology & Haematology. 2018;14:50–56.