Unit Three - Key Area 5 Flashcards
What is a pathogen?
A pathogen is a bacterium, virus or other organism that can cause disease/harm.
What are antigens?
Antigens are molecules, often proteins located on the surface of cells that trigger an immune response.
How do physical barriers prevent disease?
physically prevent the entry of infection
How does chemical defence prevent disease?
destroy pathogens before infection
What is an example of a physical barrier to disease?
Closely packed epithelial cells are found in the skin and inner linings of the digestive and respiratory systems are physical defences.
What is an example of a chemical defence to disease?
secretions such as tears, saliva, mucus and stomach acid
What do mast cells release?
histamine
What does the release of histamine do and what is the result?
Causes vasodilation and increased capillary permeability. The increased blood flow leads to an accumulation of phagocytes and clotting elements at the site of infection.
What are phagocytes?
Phagocytes are white blood cells which recognise pathogens and destroy them by phagocytosis.
What does phagocytosis involve?
the engulfing of pathogens and their destruction by digestive enzymes contained in the lysosomes.
What are cytokines?
Cytokines are protein molecules that act as a signal to specific white blood cells causing them to accumulate at the site of infection.
