Which of the following is not a common portal of exit for pathogens in humans?

The muscular system is not typically recognized as a common portal of exit for pathogens in humans. Pathogens most commonly exit the body through specific systems that are involved in excretion and secretion processes. The respiratory system serves as a route for pathogens via droplets expelled during coughing or sneezing. The gastrointestinal system can expel pathogens through feces, while the urinary system can release pathogens through urine. In contrast, the muscular system does not provide these pathways for pathogen exit, as it primarily functions in movement and support rather than in the expulsion of infectious agents. Thus, it is not associated with the mechanisms that allow pathogens to leave the host and potentially infect others.