Cilia and mucus are examples of which line of defense in the human body?

• A. Second line of defense
• B. First line of defense
• C. Third line of defense
• D. Fourth line of defense

Answer: (B)

Verified step by step guidance

1. Understand the concept of lines of defense in the human body. The human body has multiple lines of defense to protect against pathogens: the first line, second line, and third line of defense.
2. The first line of defense includes physical and chemical barriers that are always ready and prepared to defend the body from infection. These barriers include skin, mucous membranes, and secretions like mucus.
3. Cilia are tiny hair-like structures that line the respiratory tract and help move mucus and trapped particles out of the airways, preventing them from entering the body. Mucus is a sticky substance that traps pathogens and particles.
4. Recognize that cilia and mucus are part of the body's first line of defense because they act as physical barriers to prevent pathogens from entering the body.
5. Review the options given in the problem and identify that cilia and mucus are examples of the first line of defense, as they are involved in preventing the entry of pathogens into the body.