BI-2223
The breathing system
Biology · Secondary 4 · Medium · The breathing system
A student is describing how the human gas exchange system helps prevent pathogens from entering the body.
Which statement is correct?
Which statement is correct?
- Mucus traps pathogens and cilia move the mucus towards the throat to be swallowed.
- Cilia secrete antibodies that directly kill all pathogens in the air.
- Alveoli secrete thick mucus that blocks all microorganisms from entering the lungs.
- Cartilage rings around the trachea contract to crush any bacteria in the air.
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