In order for a pathogen to cause infection, it must gain entry to the body. Therefore, we must have a range of defences.
Barriers To Entry
-skin covers the surface of the body, which is a physical barrier that most pathogens find hard to penetrate.
-epithelial lining the trachea beat mucus (produced by goblet cells) which has caught pathogens up to the mouth where it can be swallowed.
-the stomach contains HCl which denatures the enzymes of a pathogen, killing it.
-epithelial lining the trachea beat mucus (produced by goblet cells) which has caught pathogens up to the mouth where it can be swallowed.
-the stomach contains HCl which denatures the enzymes of a pathogen, killing it.
Phagocytosis
-phagocytes perform phagocytosis.
-they often travel in the blood, but can move into other tissues if necessary.
-the pathogens chemical products attract the phagocytes.
-the phagocytes bind to the pathogen's surface.
-they engulf the pathogen to form a vesicle called a phagosome.
-lysosomes move towards the phagosome and fuse with it, breaking down the cell membrane.
-they digest it by breaking down the contents.
-the soluble products of the digestion are absorbed into the cytoplasm.
-they often travel in the blood, but can move into other tissues if necessary.
-the pathogens chemical products attract the phagocytes.
-the phagocytes bind to the pathogen's surface.
-they engulf the pathogen to form a vesicle called a phagosome.
-lysosomes move towards the phagosome and fuse with it, breaking down the cell membrane.
-they digest it by breaking down the contents.
-the soluble products of the digestion are absorbed into the cytoplasm.
Questions
1) What is phagocytosis? (5 marks)
2) Suggest why you may find lysosomes in the tears? (1 mark)
2) Suggest why you may find lysosomes in the tears? (1 mark)