What are the mechanical and chemical barriers of defense?

What are the mechanical and chemical barriers of defense?

• A. The first line of defense protecting the internal environment.
• B. The inflammatory response.
• C. Antibody production by plasma cells.
• D. Activation of cytotoxic T cells.

Answer: (C)

Mechanical and chemical barriers are the body's first line of defense, designed to keep pathogens from entering the internal environment. Mechanically, intact skin and mucous membranes form a physical barrier and include features like tight cell junctions, continuous shedding of skin, and cilia or mucus that help expel invaders. Chemically, secretions such as sweat and sebum on the skin, acidic gastric juice, tears, saliva, and mucus contain substances that inhibit or destroy microbes, such as enzymes and antimicrobial peptides. Together, these barriers prevent entry and protect the body before any immune cells are recruited. If a breach occurs, the inflammatory response and the adaptive immune components—antibody production by plasma cells and cytotoxic T cell activation—are engaged subsequently.

Mechanical and chemical barriers are the body's first line of defense, designed to keep pathogens from entering the internal environment. Mechanically, intact skin and mucous membranes form a physical barrier and include features like tight cell junctions, continuous shedding of skin, and cilia or mucus that help expel invaders. Chemically, secretions such as sweat and sebum on the skin, acidic gastric juice, tears, saliva, and mucus contain substances that inhibit or destroy microbes, such as enzymes and antimicrobial peptides. Together, these barriers prevent entry and protect the body before any immune cells are recruited. If a breach occurs, the inflammatory response and the adaptive immune components—antibody production by plasma cells and cytotoxic T cell activation—are engaged subsequently.