The thymus
Thymus · thymus
A gland in your upper chest that trains immune cells, largest in childhood.
What it does
The thymus lies behind the breastbone, in front of the heart. It is where young T cells, a type of white blood cell, learn to attack germs while leaving your own tissues alone. Cells that react against the body are weeded out before they leave.
Surprising fact
The thymus is largest in childhood and slowly shrinks after puberty, gradually being replaced by fat.
Why it matters
Its training role is vital early in life, which is why children born without a working thymus have severe immune problems.
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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.