Which of the following are all forms of defence that prevent the entry of pathogens into the body? (A) Cilia, sweat, saliva - HSC - SSCE Biology - Question 3 - 2012 - Paper 1

To determine which options are forms of defense that specifically prevent the entry of pathogens, we can analyze each choice:

• (A) Cilia, sweat, saliva: These are all mechanisms that help in trapping and flushing out pathogens. Cilia in the respiratory tract move mucus that traps pathogens, sweat contains antimicrobial substances, and saliva has enzymes that can break down pathogens. Thus, this option is valid.

• (B) T cells, B cells, antibodies: These are parts of the immune response that react to pathogens after they have entered the body. They do not prevent initial entry but respond to infections. Therefore, this option does not fit the criterion.

• (C) Inflammation, skin, phagocytosis: While skin acts as a primary barrier preventing entry, inflammation and phagocytosis are responses that occur after entry, serving to eliminate pathogens. Hence, this option is partially valid.

• (D) Stomach acid, mucus, lymph system: Stomach acid kills pathogens that enter through food, mucus traps pathogens, and while the lymph system helps in fighting infections, it is not a barrier to entry itself. This option includes effective defenses against pathogens.

After analyzing all options, the correct answer is (A) as it includes only those defenses that prevent the entry of pathogens.