The spleen
Spleen · lien
A fist-sized organ under your left ribs that filters old blood cells and fights infection.
What it does
The spleen sits under the left ribs, behind the stomach. It filters the blood, removing worn-out red blood cells and recycling their iron, and it is packed with immune cells that catch bacteria in the bloodstream. In emergencies it can release a reserve of blood cells.
Surprising fact
Diving mammals, such as seals, use their spleen as a store of oxygen-rich red blood cells, and human free-divers' spleens shrink slightly during a breath-hold dive to do the same.
Why it matters
Because it is soft and full of blood, the spleen can rupture after a hard blow to the left side, which is why people with glandular fever are told to avoid contact sports while it is enlarged.
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Open in the 3D atlas · Suggest a correction · Not medical advice.
3D models: Z-Anatomy & BodyParts3D (CC BY-SA 4.0 / 2.1 JP). Card text CC BY 4.0.