The first line of defence is involved in non-specific responses to pathogens to prevent them from entering the body. This type of defence against infection involves body barriers and chemical secretions.
This provides a barrier of entry of pathogens as long as the skin is intact. Any cut or abrasion in the skin will damage the skin’s shielding properties and allow pathogens access. Skin also has chemical protective mechanisms, as glands in the skin can secrete fatty acids and sweat containing salts that inhibits bacteria.
Mucus is secreted by cells lining the respiratory tract and helps trap bacteria and then sweeps them up the throat with the action of cilia, allowing the individual to cough them up and remove them, or blow them out of your nose through sneezing. Mucus also exists in the digestive tract forming a protective barrier particularly in the stomach. It is also present in the vagina to trap bacteria preventing them entering the genito-urinary tract.
Saliva present in the mouth contains lysozymes that cause bacteria to lyse or burst
Tears like saliva contain lysozymes that cause bacteria to lyse or burst.
The stomach is kept at a very low pH due to the hydrochloric acid present. The acidic environment creates unfavorable living conditions for a lot of bacteria and kills them.
Plants do not contain an immune system, but they still have nonspecific responses to prevent themselves from infection through various adapted structural features and chemical secretions.
These mechanisms include:
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