UK GCSE level age ~14-16, ~US grades 9-10 Biology revision notes re-edit 16/05/2023 [SEARCH]

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

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INDEX of biology notes on the body's defence mechanisms against infections from pathogens


(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.



INDEX of biology notes on the body's defence mechanisms against infections from pathogens


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