Non-Specific Animal Defences

• What are the body's first lines of defence?

  The skin, mucous membranes, expulsive reflex, blood clotting, and inflammation
• What is the outer layer of the skin called?

  The epidermis
• How are keratinocytes produced in the skin?

  They are produced by mitosis and then move towards the surface
• What happens to keratinocytes as they move towards the surface of the skin?

  Their cytoplasm is replaced by the protein keratin
• What role do healthy microorganisms play on the skin?

  They outcompete pathogens
• What substance does the skin produce to help protect against pathogens?

  Sebum
• What do mucous membranes in body tracts do?

  They trap and destroy pathogens using lysozyme
• What is the function of stomach acid in the body's defence?

  It helps prevent pathogens
• What is the purpose of expulsive reflexes like coughing and sneezing?

  They expel pathogen-containing mucus from the gas exchange system
• How do vomiting and diarrhoea contribute to the body's defence?

  They expel contents of the gut and any infective pathogens
• What is involved in the blood clotting process?

  Calcium ions and at least 12 factors
• What is the most important enzyme involved in blood clotting?

  Thromboplastin
• What triggers the release of thromboplastin during blood clotting?

  Damaged tissue causes platelets to release thromboplastin
• What role does serotonin play in blood clotting?

  It causes smooth muscle in blood vessels to contract
• What happens after a blood clot forms?

  It dries and forms a scab, drawing the sides of the cut together
• What is deposited under the scab during healing?

  Collagen
• What do stem cells from the epidermis do during healing?

  They form new skin
• What happens to blood vessels during inflammation?

  They become leaky to form more tissue fluid
• What is the role of mast cells in inflammation?

  They detect microorganisms and release histamine and cytokines
• What effect do histamines have during inflammation?

  They increase tissue fluid and promote healing
• What are cytokines?

  Protein-based cell signalling molecules that aid immune responses
• How do cytokines assist during inflammation?

  They stimulate the movement of cells like phagocytes towards sites of inflammation
• What are some additional components of the body's first lines of defence?

  Eyelashes, earwax, ear hair, acidic vagina, and tears
• How does lysozyme in body secretions help prevent pathogens?

  It traps and destroys pathogens
• What is the cascade response in blood clotting?

  • Involves a series of reactions triggered by thromboplastin
  • Leads to the formation of fibrin
  • Fibrin forms a network trapping platelets
  • Results in a clot that plugs the hole
• What is the role of phagocytes in the immune system?

  They are a second defense that kills pathogens before they can reproduce.
• What type of white blood cells are neutrophils?

  Neutrophils are a type of phagocyte.
• Where are neutrophils made?

  Neutrophils are made in the bone marrow.
• What is a characteristic feature of neutrophils' nuclei?

  Neutrophils have a multi-lobed nucleus.
• What type of cytoplasm do neutrophils have?

  Neutrophils have granular cytoplasm containing lysosomes.
• Where do neutrophils travel in the body?

  Neutrophils travel in the blood and tissue fluid.
• In which type of tissue can neutrophils be found?

  Neutrophils can be found in epithelial tissue, such as the lung.
• How long do neutrophils typically live?

  Neutrophils are short-lived.
• What percentage of white blood cells do neutrophils make up?

  Neutrophils make up around 40% of white blood cells (WBCs).
• How quickly do neutrophils arrive at a site of infection?

  Neutrophils arrive at a site of infection quickly.
• What is the shape of macrophages' nuclei?

  Macrophages have a kidney bean-shaped nucleus.
• What is a key feature of macrophages' cytoplasm?

  Macrophages have non-granular cytoplasm.
• How do macrophages travel in the body?

  Macrophages travel in the blood as monocytes before developing in lymph nodes.
• How long do macrophages typically live?

  Macrophages are longer-lived than neutrophils.
• What is the function of the Major Histocompatibility Complex (MHC) in macrophages?

  MHC forms to become an Antigen Presenting Cell.