Phagocytosis

• What is the first line of defence to disease?

  Barriers to entry
• Skin


  Is a physical barrier to most pathogens as they find it hard to penetrate
• Epithelia


  Is covered in Mucus as the next line of defence; this stops pathogens entering the lungs as it sticks to the mucus; Pathogens are then transported by Cilia up the Trachea to be swallowed into the stomach
• HCl Acid in the stomach…

  Has a low enough pH that most enzymes and pathogens are denatured before the organisms are killed
• What does “Phago” mean in greek?

  To devour
• What does “Cytosis“ mean in greek?

  Cell
• What is Phagocytosis?


  The cellular process of engulfing solid particles by the cell membrane to form an internal Phagosome in Phagocytes
• Where can Phagocytosis?

  In the Immune System as a non-specific second line of defence against pathogens
• What is the first stage in Phagocytosis?

  Phagocyte detects chemicals released by foreign intruder
• What is the second stage of Phagocytosis?

  Phagocyte moves up the concentration gradient towards the intruder
• What is the third stage of Phagocytosis?

  The Phagocyte adheres to the foreign cell and engulfs it in a vacuole by the invagination of the cell membrane
• What is the fourth stage of Phagocytosis?

  Lysosomes (Organelles rich in digestive enzymes found in the Phagocytes cytoplasm) fuse into the vacuole and release their content into it to form a Phagolysosome
• What is the fifth stage of Phagocytosis?

  The foreign microbe is digested by the enzymes and the breakdown products are either egested or absorbed by the Phagocyte