Which of the following is an example of a portal of exit?

The respiratory system serves as a primary portal of exit in the context of infection control and transmission of pathogens. This is because respiratory pathogens can exit the body through droplets produced during coughing, sneezing, or even talking. When these droplets are expelled from an infected individual, they can subsequently travel through the air and potentially enter the respiratory tracts of others, leading to the spread of infections such as the common cold, flu, or COVID-19.

In contrast, while options such as a cut on the skin, an open wound in the mouth, and the gastrointestinal (GI) tract can also serve as exit points for pathogens, they are generally categorized under direct contact or different modes of transmission rather than the respiratory route. This highlights the respiratory system's unique role as a portal of exit, particularly in the transmission of airborne diseases. Understanding these portals is crucial for implementing appropriate infection control measures in healthcare settings.