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Human Body Study

Thymus

A gland in the upper chest, behind the breastbone — the training school for one major class of immune cell.

The lymphatic and immune system A stylised body with the lymphatic organs placed at their anatomical positions, plus two concept panels for the functional arms — innate immunity (phagocytes eating pathogens) and adaptive immunity (lymphocytes and antibodies). Each label links to the article for that part. Innate immunity fast frontline: phagocytes ingest pathogens Adaptive immunity specific and remembered: lymphocytes and antibodies Tonsils Thymus Lymph nodes Spleen Lymphatic vessels Bone marrow Lymphatic organs and lymph vessels, plus the two arms of the immune response — schematic.

What it does

Section titled “What it does”

T lymphocytes (T cells) mature here, learning to attack foreign threats while sparing the body’s own tissue. Cells that fail this test are eliminated.

Lifespan note

Section titled “Lifespan note”

The thymus is largest and most active in childhood and slowly shrinks after puberty, gradually being replaced by fat.

Key idea

Section titled “Key idea”

The thymus does its essential work early in life — building the T-cell repertoire that defends the body for decades afterward.