Animal defences

• What are primary defences?

  Non-specific barriers preventing pathogen entry
• What are secondary defences?

  Actions of phagocytes to kill pathogens
• Why is skin considered an effective barrier?

  It provides a waterproof physical barrier
• What type of cells make up the epidermis?

  Keratinocytes
• How are new skin cells produced?

  By mitosis at the base of the epidermis
• What occurs during keratinisation?

  Cells dry out and become keratinised
• What happens to keratinised cells over time?

  They fall off after about a month
• Why is blood clotting important?

  It prevents excessive blood loss and infection
• Why is blood clotting considered a complex process?

  Clots must form only when needed
• What triggers the blood clotting process?

  Platelets and damaged cells release clotting factors
• How does a scab form?

  A mesh of fibrin forms over the wound
• How does the skin repair itself after a wound?

  Collagen is deposited and stem cells divide
• How do scars form?

  Collagen replaces lost tissue in deep wounds
• What are mucous membranes?

  Thin layers of epithelial tissue for protection
• Where are mucous membranes found?

  In respiratory, digestive, excretory, reproductive systems
• How do mucous membranes protect against pathogens?

  Goblet cells secrete mucus to trap pathogens
• What happens to trapped pathogens in the respiratory system?

  Mucus moves up the trachea to be expelled
• What are expulsive reflexes?

  Automatic responses that expel foreign objects
• What causes sneezing?

  Irritation of nasal mucous membranes
• What causes coughing?

  Irritation of mucous membranes in the respiratory tract
• What is lysozyme?

  An enzyme that breaks down bacterial cell walls
• How do "helpful" bacteria protect us from infection?

  They outcompete harmful pathogens
• What is the role of the microbiome in infection prevention?

  It maintains a balanced environment against infections
• What is histamine?

  A cell-signalling molecule released by mast cells
• What effect does histamine have on blood vessels?

  It causes vasodilation and increased permeability
• What are the four symptoms of inflammation?

  1. Redness
  2. Swelling
  3. Heat
  4. Pain
• Why does inflamed tissue appear red?

  Histamine causes vasodilation, increasing blood flow
• What causes swelling in inflamed tissue?

  Increased capillary permeability allows fluid accumulation
• Why is it beneficial for extra fluid to drain into the lymphatic system?

  It helps trigger a specific immune response
• What role do lymphocytes play in inflammation?

  They help trigger a specific immune response