- The immune system
- The body's defence system against disease. Consists of mainly white blood cells.
- The lymph and blood vessels. These transport pathogens and leukocytes all over the body
- The lymph nodes. These contain millions of phagocyte and lymphocyte cells, which identify and remove pathogens from lymph
- The spleen. This contains millions of phagocyte and lymphocyte cells, which identify and remove pathogens from blood
- The thymus. This is where blood stem cells are differentiated into T-lymphocytes.
- The white blood cells or leukocytes are derived from stem cells, which are produced in huge numbers in the bone marrow.
- Three lines of defence: 1.Barriers - the skin and associated chemicals stop microbes entering the body. 2. The non-specific immune system - phagocytes quickly destroy microbes that pass the first line of defemnce 3.The specific immune system - lymphocytes kill any microbes that pass the second line of defence, and remain on guard for future attacks