Destroy bacteria, viruses, fungi and protozoa. Principle cells of the lymphatic system. Involved in clotting. Phagocytes and lymphocytes remove foreign organisms and cell debris. Synthesis of all blood cell types.
B cells mature here.
Stores both red and white blood cells. Filters and clears out old red or white blood cells. T cells mature in the thymus. Red area due to increased blood flow. Hot due to increased metabolism and blood flow.