Entry doors of microorganisms into the human organism, bacteria, viruses. The part of the illustration on the 2/3 left explains that the bacteria and viruses are in our environment (air, water, soil, objects, food). They are also present on the surface of our body on the skin and penetrate our body through the external orifices, nose, mouth, urethra, vagina and rectum. Thus, microorganisms are found in the nasal, oral, lung, ? sophage and stomach, intestinal tract, and pelvic organ exit doors. They can cross the skin barrier and penetrate the body through a wound, but also through the mucous membranes. Our body is therefore inhabited by micro-organisms. This coexistence with some is very beneficial