Differences between primary and chemical barrier
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Answer:
These barriers provide a physical block against pathogens from entering the immune system. The largest barrier comprises of the skin, which has a large surface area and covers the majority of the external surfaces of the body.
The mucous membranes of the mouth, respiratory tract, GI tract and urinary tract also line the the areas of the body that are in contact with the external environment, preventing pathogens from crossing.
The final physical barrier of the innate system is the bronchial cilia. These cells form a mucociliary escalator which allows gradual removal of pathogens from the respiratory system.There are two main chemical barriers to infection, the relatively low pH of parts of the body and antimicrobial molecules. The following areas of the body have an acidic pH:
Skin – pH 5.5
Gastric acid – pH 1-3
Vagina – pH 4.4
These pHs create a hostile environment that pathogens struggle to thrive in and certainly in the case of gastric acid, can denature the proteins of pathogens.
There are also a variety of innate antimicrobial molecules throughout the body which can aid in the destruction of pathogens:
IgA – present in tears, saliva and mucous membranes
Lysozyme – present in sebum, perspiration and urine
Mucus – present in mucous membranes
Beta-defensins – present in epithelia
Pepsin – present in the gastrointestinal tract