The thymus
The thymus is a small, irregular-shaped
Structure of the thymus
The thymus is divided into 2 main parts – a right lobe and a left lobe. Each lobe is divided into smaller sections called lobules that give the thymus its bumpy appearance. Each lobule is made up of a centre part (called the medulla) and an outer layer (called the cortex). A thin covering (capsule) surrounds and protects the thymus.
The thymus is mainly made up of
The thymus is large in newborns and toddlers, and is most active during childhood and adolescence. It grows to its largest size during puberty. After puberty, the thymus slowly shrinks as the epithelial cells begin to be replaced by fat tissue.
By late adulthood, most of the thymus is made up of fat tissue.
What the thymus does
The thymus makes T cells (called T lymphocytes) that travel throughout the body to help fight infection, disease and foreign substances.
Lymphocytes travel from the
The thymus also makes
- thymopoietin
- thymulin
- thymosin
- thymic humoral factor
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