Human Defence Systems Against Pathogens

The video explains the body's defense mechanisms against pathogens. It starts with the skin, the largest organ, acting as a physical barrier. The respiratory system uses mucus and cilia to trap and expel invaders. Blood clots prevent infections in wounds, while stomach acid kills ingested pathogens. Friendly bacteria in the intestines also play a role. If pathogens bypass these barriers, the second line of defense, including white blood cells and antibodies, takes over to protect the body.

Which organ is the largest and acts as a physical barrier against pathogens?

• Brain

• Skin

• Heart

• Liver

What substance do sebaceous glands secrete to prevent pathogen growth?

• Water

• Acids

• Enzymes

• Proteins

How does the respiratory system help in defending against pathogens?

• By secreting acids

• Through nasal hair and mucus

• By producing antibodies

• Through skin barriers

What role does stomach acid play in the body's defense?

• It neutralizes toxins

• It kills harmful microorganisms

• It digests food

• It absorbs nutrients

What is the function of white blood cells in the body's defense system?

• They produce enzymes

• They secrete acids

• They form a physical barrier

• They hunt and destroy pathogens