• The circulatory and lymphatic systems
Circulatory system Lymph, lymph nodes, white cells, tonsils
Blood pressure, hardening and clogging of arteries

• The immune system fights infections from bacteria, viruses, fungi.
White cells, antibodies, antigens
Vaccines, communicable and non-communicable diseases, epidemics
Bacterial diseases: tetanus, typhoid, tuberculosis; antibiotics like penicillin, discovered by Alexander Fleming
Viral diseases: common cold, chicken pox, mononucleosis, rabies, polio, AIDS