Definition and Physiology of Illness   STDs, also known as sexually transmitted diseases, are infections and are spread from one person to another via the mucous membranes of the sexual organs, as well as bodily fluids. Transmission of these diseases can also occur via the mucous membranes in the throat, mouth and eyes. The term STD actually encompasses a number of diseases rather than just one, as there are more than 20 different types, with their infectious agents being bacteria, viruses, or parasites. https://medlineplus.gov/sexuallytransmitteddiseases.html  The mucous membranes that...