Which one of the following not acts as physiological barrier to protect the body from inhibiting microbial growth ?

Skin on our body .

The correct answer is Option (2) - Skin on our body .

Innate immunity is non-specific type of defence, that is present at the time of birth. This is accomplished by providing different types of barriers to the entry of the foreign agents into our body. Innate immunity consist of four types of barriers. These are —

Physical barriers : Skin on our body is the main barrier which prevents entry of the micro-organisms. Mucus coating of the epithelium lining the respiratory, gastrointestinal and urogenital tracts also help in trapping microbes entering our body.

Physiological barriers : Physiological barriers include various substances and conditions within the body that inhibit microbial growth. For example, the acid in the stomach creates an unfavorable environment for many microorganisms. Saliva in the mouth, tears from the eyes, and other bodily secretions also contain substances that help in preventing microbial growth.