Describe how the body's natural defences prevent pathogens from entering the bloodstream.

AQA GCSE Biology (8461) — 4.3.1 Communicable diseases · Describe · 4 marks · View as Markdown

Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).

Model answer (4 marks)

Skin acts as a physical barrier, preventing pathogens from entering the body.

Mucus in the nose, trachea and airways traps pathogens and microorganisms.

Cilia move the mucus (and trapped pathogens) away from the lungs towards the throat.

Stomach acid (hydrochloric acid) kills pathogens that are swallowed.

Examiner tips

  • Use the exact terms: skin, mucus, cilia, stomach acid. Show the sequence of barriers. Keep each point short and clear.
  • common_mistakes
  • :
  • Mixing up the order of the barriers. Using vague words like "body’s defence" instead of specific mechanisms.

Mark scheme (4 marks)

  1. Skin acts as a physical barrier / prevents pathogens entering the body
  2. Mucus in the nose / trachea / airways traps pathogens / microorganisms
  3. Cilia move mucus (and trapped pathogens) away from the lungs / towards the throat
  4. Stomach acid / hydrochloric acid kills pathogens that are swallowed

Key terms in this question

pathogen

Related

More Communicable diseases questions

▶ Try answering this question with AI marking (free) →