Question

Anatomic barrier to disease is:
A) Skin
B) Mucous membrane
C) Mucus and cilia
D) All of the above

Answer 1

Hint: Despite being exposed to the outer environment containing many infectious agents, we hardly get infected by them, this is because our body is able to protect itself, this is called immunity. It is of two types- innate immunity (birth immunity) and acquired immunity.

Complete answer: Innate immunity is that immunity which we get from our birth it is a nonspecific type of immunity (that means it is not selective towards any particular group of microbes, it resist all kind of pathogens which comes on its way) so it is accomplished by different type of barriers:
1) Physical barrier: It includes skin, mucous lining of the respiratory tract, gastrointestinal tract, and urogenital tract.
2) Physiological barrier (Anatomical barrier): It includes acid in the stomach, saliva in the mouth, tears from eyes, All these have antimicrobial properties.
3) Cellular barrier: It consists of different kinds of leucocytes like PMNL (Polymorpho-nuclear leukocytes) and monocytes and natural killer cells. These cells destroy and phagocytose the microbes.
4) Cytokine barrier: In this kind of barrier, virus-infected cells release a protein called interferons which protect the non-infected cells from further virus attack.
So, the correct answer is option (D).
Additional Information:
There is another type of immunity besides innate immunity and that is acquired immunity. Unlike innate immunity, it is a specific type of immunity, and its main characteristics is memory. This kind of Immunity has a memory of its first encounter with pathogens. And the response shown by our immune system is called primary response which is of very low intensity but when the same microbe attacks for the second time, the role of memory comes into the picture. It shows a highly intensified secondary response. This is due to the formation of Antibody after the first encounter with Antigen (microbes).

Note: Physiological or anatomical barrier Include the immunity developed by our physiology like Temperature, pH, etc. Temperature is a very important factor for the growth of any kind of microbes. They also grow under a particular temperature and below or above that temperature, they cannot grow.
Anthrax-causing bacteria cannot grow in the chicken body due to high temperature there, in the same way, temperature acts as a barrier for many microbes for humans also. Just like temperature, microbes need a particular pH to grow and survive and if that condition is not provided, they will die and we will be protected. A very acidic pH in our stomach protects us from several microbes but in infants, pH is more that is they have a less acidic environment in their stomach and hence they are prone to infection.