Chapter 40, Problem 1TY

Summary Introduction

Introduction:

Barriers could be natural and biological barrier to immune system. Natural barriers are those which protect body from organism causing infection like skin, mucous membrane, ear was, mucus,etc.Biological barrier are those having antimicrobial molecules throughout the body that helps isn destruction of pathogens like saliva, sebum, urine,etc.

Answer to Problem 1TY

Option (e) antibodies

Explanation of Solution

Explanation/justification for the correct answer:

Option (e) antibodies. Antibodies are produced from an immune system when pathogens have crossed the first line of defense or the barrier. It is usually produced by immune system that stops antigens like bacteria, virus from harming the body.

Explanation for incorrect answer:

Option (a) skin. Skin is the outermost covering which is the primary barrier protecting from the entry of microorganisms. As this is a barrier defense, the answer is incorrect.

Option (b) secretions from skin glands. Secretions from the skin like sweat lower the pH in the skin or contain toxic lipids and wash away the microbes. As this is a barrier defense, the answer is incorrect.

Option (c) Exoskeleton. It is external skeleton that protects and supports animal body when compared to internal skeleton that protects internal organs. It is a natural barrier. So, this answer is not correct.

Option (d) mucus. The layer of the gastrointestinal tract, respiratory tract, reproductive tract, ears, nose have mucus layer which traps dust or microbes and removes them. The saliva moves the contaminated mucous downwards to the stomach where the environment is acidic destroying the microbes. So, this answer is incorrect.

Conclusion

The antibodiesis not example of barrier defense asit is acquired part of immune system and not natural barrier. Hence, the correct answer is option (e).