Final answer:
Human ears, skin, nose, and throat are part of the body's defense system that incorporates both physical barriers, such as the epidermis and mucous membranes, and chemical barriers like secretions that protect against pathogens.
Step-by-step explanation:
The ears, skin, nose, and throat are essential components of the human body's defense system against pathogens.
The skin acts as a significant physical barrier with layers like the epidermis and dermis, which include glands that create an environment hostile to many pathogens. Moreover, the skin is home to normal flora, nonpathogenic bacteria that also help protect the body by outcompeting harmful microbes.
The nose has hairs and mucous membranes with cilia that trap and move pathogens to the mouth, preventing them from entering the upper respiratory tract. Similarly, the ears are protected by hairs and wax that block foreign particles.
The oral cavity, or mouth, has its own mechanisms of protection, including saliva that can break down invading microorganisms.
Lastly, the throat, part of the respiratory system, is lined with mucus that traps pathogens, while the acidic environment in the stomach serves as a chemical barrier to ingest pathogens.