Which body part is involved in a non-mechanical body defense?

The nose plays a crucial role in the body’s non-mechanical defense mechanisms, primarily through its function in the respiratory system. It serves as the first line of defense against pathogens and harmful particles in the air. The nasal passages are lined with mucous membranes that trap allergens, dust, and microorganisms, preventing them from entering the lower respiratory tract. Additionally, the nose is equipped with cilia, tiny hair-like structures that help move trapped pathogens out of the nasal cavity.

This non-mechanical defense function is complemented by the presence of immune cells in the nasal mucosa that can initiate an immune response when encountering pathogens. The respiratory mucosa also contains antimicrobial substances that can neutralize certain microbes as they are inhaled.

While other options, such as the skin, stomach, and liver, do play roles in the body’s defense system, they primarily involve mechanical, biochemical, or metabolic processes. The skin serves largely as a physical barrier, the stomach uses acidic secretions to destroy pathogens, and the liver plays a role in detoxification and metabolism of substances, rather than directly serving as a non-mechanical defense against inhaled pathogens. Thus, the nose is uniquely positioned to actively filter and protect against airborne threats through non-mechanical means.