Page 54 - Science Course 2 (Book 1)

Mo2-L3c: How Does the Body Protect Itself From Harmful Invaders?

Humans make billions of different types of antibodies.
Key Concept
Infectious diseases are caused by How Does the Body Protect Itself From Harmful
pathogens, such as bacteria and Invaders?
viruses, and are usually How does the body defend itself from harmful
contagious. invaders?

A noninfectious disease is caused by the environment
or a genetic disorder.

Example Of Disease
Infectious Disease
Noninfectious
Disease Pathogen Disease

cold virus cancer

AIDS virus diabetes

strep throat bacteria heart disease

chicken pox virus allergy

SUMMARY
The body’s first line of defense against viruses,
bacteria, and harmful substances is the skin and How Does the Body Protect Itself From Harmful
mucus which prevent toxins and other substances Invaders?
from entering the body. Immune cells detect and destroy viruses,
bacteria, and other foreign substances.
The second line of defense is the immune response
in which white blood cells attack and destroy
harmful substances.

The third line of defense is immune cells which make
antibodies that destroy harmful substances.

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