disease

• how can you identify red blood cells on a blood smear?

  they are naturally stained red and don't have a nucleus
• how can you identify neutrophils on a blood smear?

  multi-lobed nucleus and a grainy cytoplasm
• how do you identify lymphocytes on a blood smear?

  much smaller than a neutrophil. The nucleus takes up most of the cell --> little cytoplasm to be seen + not grainy --> can't distinguish between T or B lymphocytes on a light microscope
• how do you identify a macrophage on a blood smear?

  biggest white blood cell, and has a non-grainy cytoplasm
• what stain is used for a blood smear and why?

  Wright stain (differential stain). It is used to differentiate and identify different types of blood cells --> it stains nuclei
• why does a neutrophil have a multi-lobed nucleus?

  flexibility --> can squeeze between other cells
• which organelle do lymphocytes have in large numbers and why?

  mitochondria - for protein synthesis - to produce antibodies
• what is phagocytosis?

  process of engulfing and digesting foreign particles or pathogens
• when a pathogen invades the body, the antigens on its cell surface are identified as foreign, which activates cells in the immune system
• steps of phagocytosis:

  1. a phagocyte recognises the antigens on the pathogen
  2. the membrane and the cytoplasm move around the pathogen, engulfing it. Opsonins help by attaching to the antigens to aid phagocytosis
  3. pathogen is now sealed in a vesicle (phagosome) in the pathocyte's cytoplasm'
  4. a lysosome fuses with the phagosome to form a pahgolysosome --> digestive enzymes in the lysosome break down the pathogen
  5. the phagocyte then present the pathogen's antigens. It sticks the antigens on its surface to activate other immune system cells --> this is acting as an antigen-presenting cell