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Body defences: 3. Chemical ways our body defend itself against pathogens

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There are various sections to work through, after 1 they can be read and studied in any order.

Sub-index of notes: Our body's defence mechanisms against infections from pathogens, help from vaccines & drugs


(3) How do our bodies defend themselves against infectious diseases?

Chemical protection by killing pathogens

Our eyes produce a chemical called lysozyme in tears, that kills bacterial microorganisms on the surface of the eye.

Lysozymes are enzymes that break down the cell walls of bacteria, so destroying the bacteria on the surface of the eye.

Lysozymes are found in several secretions produced by the body.

The stomach produces strong hydrochloric acid, an acid that kills most pathogens, and a safe distance from the sensitive tissue of the mouth and tongue!

Your stomach contains quite concentrated strong hydrochloric acid which kills the majority of pathogenic bacteria that get well beyond the mouth - sadly not all of them at times!

The saliva produced in your mouth contains molecules that can kill some of the pathogens that enter the mouth.

 

Beyond the stomach

Not all the remaining pathogens that reach the stomach from the mouth are killed by the hydrochloric acid.

Some pathogens enter the intestines and have to compete with the 'local' bacteria for food to survive.

Your gut is full of bacteria - the gut is their natural habitat.

As well as acting as a physical barrier, your skin also has sebaceous glands that secrete antimicrobial molecules that can kill pathogens.

The sebaceous glands are an 'offshoot' of the hair shaft, out of which the hair grows.

These chemical defences are non-specific and can counteract a variety of types of pathogens


Learning objectives for this section on our body's chemical defences against pathogens

Be able to describe chemical ways in which the body defends itself against pathogens.

Know that lysozyme in tears protects against pathogens potentially infecting our eyes.

Know about the action of the strong acid, hydrochloric acid in our stomach that kills bacteria.

Know that our skin has sebaceous glands that secrete antimicrobial molecules to kill bacteria.

  • Be able to explain how the human body can be effective against attack from pathogens, including:
    • The body has different physical and chemical ways of protecting itself against pathogens.
    • b) Chemical defence hydrochloric acid in the stomach, lysozymes in tears
      • Chemical protection by killing pathogens

      • In tears our eyes produce chemicals called lysozymes that kill bacterial microorganisms on the surface of the eye.

      • Your stomach contains quite concentrated hydrochloric acid which kills the majority of pathogenic bacteria - sadly not all of them at times!


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