Answer :
The primary defensive barriers of the human body are chemical (such as gastric juice and saliva), physical (like the skin and mucous membranes), and biological (such as the bacterial flora in the intestine).
1. The gastric juice is considered a chemical defense because it contains hydrochloric acid and enzymes that help break down food and kill ingested pathogens. The acidic environment created by the gastric juice serves as a hostile environment for many harmful microorganisms, preventing them from causing infections.
2. Saliva is also a chemical defense because it contains enzymes like lysozyme that can destroy the cell walls of certain bacteria, inhibiting their growth. Additionally, saliva helps to lubricate and cleanse the mouth, washing away food particles and bacteria that could potentially enter the body through ingestion.
In summary, both gastric juice and saliva act as chemical defenses by containing substances that help kill or inhibit the growth of pathogens, thus protecting the body from harmful microorganisms that could cause infections.
