Overview
This lecture covers the main mechanisms by which pathogens enter (portals of entry) and leave (portals of exit) the human body, emphasizing their routes and significance in disease transmission.
Portals of Entry
- Portals of entry are the ways pathogens gain access to the body.
- Pathogens usually enter through the portal closest to their target tissue.
- The most common portals of entry are mucous membranes of the respiratory, digestive, and genitourinary systems.
- Respiratory system is highly vulnerable due to constant inhalation of airborne microbes.
- Digestive system is exposed to pathogens through food and drink.
- Genitourinary system is a frequent entry point for sexually transmitted and urinary tract infections.
- Other portals include the nose, mouth, placenta (for certain infections), eyes (via conjunctiva), urethra, anus, vagina, and ears.
- The skin can be a portal if broken; some pathogens can enter through intact skin but it is rare.
- The Parenteral Route involves direct access through broken skin or mucous membranes (e.g., needle sticks, insect bites, cuts).
Portals of Exit
- Portals of exit are the ways pathogens leave the host to infect new individuals.
- Pathogens usually exit the same way they entered—for example, respiratory pathogens leave via the respiratory system.
- Examples of portals of exit are feces, saliva, tears, breast milk, skin, blood (via wounds or insect bites), and ear wax.
- The placenta can serve as both a portal of entry and exit for some pathogens.
- Effective exit is critical for pathogens to spread and continue their lifecycle.
Key Terms & Definitions
- Portal of Entry — The site through which a pathogen enters the host.
- Mucous Membrane — Moist tissue lining body cavities that are open to the environment; common entry points.
- Parenteral Route — Entry of pathogens via breaks in the skin or mucous membranes, bypassing the usual barriers.
- Portal of Exit — The route by which a pathogen leaves the host to infect others.
Action Items / Next Steps
- Review the specific pathogens able to cross the placenta (e.g., TORCH infections).
- Prepare to discuss examples of diseases for each portal of entry and exit in the next session.