NEET 2026
- Exam
- NEET
- Year
- 2026
- Subject
- Biology
- Chapter
- Chapter
NEET 2026 · Biology · Chapter
A human child is born with certain non-specific defense mechanisms...
A human child is born with certain non-specific defense mechanisms that prevent the entry of pathogens. Which of the following represents a physical barrier of this innate immune system?
Options
- AHydrochloric acid in the stomach and saliva in the mouth
- BIntact skin and mucus coating of the respiratory tract
- CNatural killer cells and macrophages in the blood
- DInterferons secreted by virus-infected cells
Correct answer
B. Intact skin and mucus coating of the respiratory tract
Step-by-step solution
Innate immunity consists of four types of barriers:
Physical barriers: Skin on our body is the main barrier which prevents the entry of micro-organisms. The mucus coating of the epithelium lining the respiratory, gastrointestinal, and urogenital tracts also helps in trapping microbes entering our body.
Physiological barriers: Acid in the stomach, saliva in the mouth, and tears from the eyes prevent microbial growth.
Cellular barriers: Certain types of leukocytes (WBC) of our body like polymorphonuclear leukocytes (PMNL-neutrophils), monocytes, and natural killer cells (a type of lymphocyte) in the blood, as well as macrophages in tissues, can phagocytose and destroy microbes.
Cytokine barriers: Virus-infected cells secrete proteins called interferons which protect non-infected cells from further viral infection.
Thus, intact skin and mucus coating represent the physical barriers of the innate immune system.
Answer: Intact skin and mucus coating of the respiratory tract
Physical barriers: Skin on our body is the main barrier which prevents the entry of micro-organisms. The mucus coating of the epithelium lining the respiratory, gastrointestinal, and urogenital tracts also helps in trapping microbes entering our body.
Physiological barriers: Acid in the stomach, saliva in the mouth, and tears from the eyes prevent microbial growth.
Cellular barriers: Certain types of leukocytes (WBC) of our body like polymorphonuclear leukocytes (PMNL-neutrophils), monocytes, and natural killer cells (a type of lymphocyte) in the blood, as well as macrophages in tissues, can phagocytose and destroy microbes.
Cytokine barriers: Virus-infected cells secrete proteins called interferons which protect non-infected cells from further viral infection.
Thus, intact skin and mucus coating represent the physical barriers of the innate immune system.
Answer: Intact skin and mucus coating of the respiratory tract