5.2 - Phagocytosis

• phagocytes


  A type of white blood cell that carry out phagocytosis

  found in the blood and tissues
• types of phagocytes


  neutrophils - stay in blood

  monocytes - in bloodstream

  macrophage - in tissues
• what are neutrophils?


  the most abundant type of white blood cell

  one of four types of granulocytes
• appearance of neutrophils


  cytoplasm appears granular

  has a lobed nucleus
• What happens when neutrophils are activated


  they become highly mobile and amoeboid-like

  they're attracted by microbial chemicals & cytokines (proteins in cell signalling) expressed by macrophages and damaged endothelial cells
• chemotaxis


  movement to a site based on a gradient in chemical signals
• phagocytosis


  process by which phagocytes engulf and destroy pathogens
• What is the process called that involves the engulfing of pathogens by phagocytes?

  Phagocytosis
• How are phagocytes attracted to pathogens?

  By a chemoattractant released from the pathogen
• What do phagocytes have on their surface membrane to recognize pathogens?

  Cell receptors that recognize chemicals
• What happens when a phagocyte engulfs a pathogen?

  A phagosome is formed
• What do lysosomes do after migrating towards the phagosome?

  They fuse with the phagosome
• What happens to the soluble products from the breakdown of pathogens?

  They are absorbed into the cytoplasm or leave by exocytosis
• What do lysosomes release to destroy pathogens?

  Lysozymes that hydrolyze cell walls
• What role does the phagocyte play after presenting some of the pathogen's antigens?

  It becomes an antigen-presenting cell
• What can an antigen-presenting cell stimulate?

  A cell-mediated response