Portals of entry are the areas of the body through which a pathogen can enter (e.g., skin, mucous membranes, tissues, and placenta), while portals of exit are the parts of the body from which a patient can transmit the disease (e.g., upper respiratory system, bodily fluids, and stool).
A portal of entry is the area of the body through which a pathogen can enter. Portals of entry include skin, mucous membranes, tissue, and placenta. The skin is the largest organ of the body and a common portal of entry. Pathogens can gain entry through any opening in the skin, including hair follicles, sweat gland ducts, punctures, or cuts. All mucous membranes of the body are susceptible to infection. The mucous membranes line the respiratory tract, gastrointestinal tract, the genitourinary tract, and conjunctiva, which is the membrane that covers the eyeballs and lines the eyelids. Examples of major sites of entry are the mucous membranes of the gastrointestinal and respiratory tracts, as well as those of the reproductive system.
A portal of exit is the area of the body through which a pathogen can be transmitted to others or to the environment. Some of portals of exit are the upper respiratory system, bodily fluid, and stool. Typically, the portals of exit relate to the infected portion of the body. Pathogens can use the same portal for entry and exit. The gastrointestinal and respiratory tracts are the most common portals of exit. An airborne pathogen can travel from the cough or sneeze of an infected person via the mouth or nose, respectively, and enter the nose or mouth of another person.