Human defences

• What is the primary function of the nonspecific defense system?

  To prevent pathogens from entering the human body
• What are the four main parts of the nonspecific defense system?

  1. Skin
  2. Nose (hair and mucus)
  3. Trachea and bronchi (cilia)
  4. Stomach (hydrochloric acid)
• What is the role of the skin in the nonspecific defense system?

  The skin forms a protective layer covering the body
• Why is the outer layer of the skin difficult for pathogens to penetrate?

  It consists of dead cells
• What substance does the skin produce that can kill bacteria?

  Sebum
• What happens when the skin is damaged?

  The skin scabs over to prevent pathogen entry
• Which body openings are not covered by skin and can allow pathogen entry?

  The nostrils and the mouth
• How does the nose help prevent pathogens from entering the body?

  It contains hair and mucus that trap pathogens
• What are cilia and what is their function in the respiratory system?

  Cilia are tiny hairs that trap pathogens and move mucus upwards
• What happens to mucus that traps pathogens in the respiratory system?

  It is moved upwards towards the throat and swallowed
• How does the stomach defend against pathogens?

  It contains hydrochloric acid that kills pathogens
• What is a common disease caused by a pathogen that can be present in food?

  Salmonella food poisoning
• What is the role of hydrochloric acid in the stomach?

  To kill pathogens before they enter the digestive system
• What is the main purpose of the immune system?

  To protect us against pathogens
• What does the nonspecific defense system do?

  It stops pathogens from entering the body
• What can still happen despite the nonspecific defense systems in place?

  Pathogens can still enter the body and cause serious disease
• What happens when the skin is damaged?

  Pathogens can invade the body and enter the bloodstream
• How do pathogens affect healthy tissue?

  They can multiply and damage healthy tissue
• What are toxins?

  Chemicals released by bacteria that make us feel unwell
• What are the two main functions of the immune system?

  To destroy pathogens and protect against future infections
• What type of cells are involved in the immune system?

  White blood cells
• What is the first function of white blood cells?

  To ingest and destroy pathogens
• What does the term "ingest" mean in the context of white blood cells?

  To take in pathogens
• What is the process called when white blood cells ingest pathogens?

  Phagocytosis
• How do white blood cells destroy pathogens after ingestion?

  By using enzymes
• What are antibodies?

  Protein molecules produced by white blood cells
• How do antibodies function in the immune response?

  They stick to pathogens and trigger their destruction
• What is a key characteristic of antibodies?

  They are specific
• What happens when a person catches measles in relation to antibodies?

  They develop antibodies specifically against the measles virus
• What are antitoxins?

  Chemicals produced by white blood cells that stick to toxins
• What is the role of antitoxins in the immune response?

  They prevent toxins from damaging cells
• What are the main functions of the immune system?

  • Destroys pathogens
  • Protects against future infections
• Describe the process of phagocytosis.

  1. White blood cells detect chemicals from pathogens
  2. They move towards and ingest the pathogens
  3. Enzymes are used to destroy the pathogens
• What is the difference between antibodies and antitoxins?

  • Antibodies:
  • Specific to pathogens
  • Trigger destruction of pathogens
  • Antitoxins:
  • Bind to toxins
  • Prevent damage to cells
• How do white blood cells protect us against toxins?

  • They produce antitoxins
  • Antitoxins bind to toxins and prevent cell damage
• What is tobacco mosaic virus also known as?

  TMV
• What types of plants can be infected by tobacco mosaic virus?

  A number of different plant species, including tomatoes
• What effect does tobacco mosaic virus have on the leaves of plants?

  It causes the leaves to discolor in a mosaic pattern
• How does the discoloration caused by tobacco mosaic virus affect the plant's growth?

  It reduces the rate of photosynthesis, leading to reduced growth
• What causes rose black spot?

  A fungus