Which one of the following not acts as physiological barrier to protect the body from the entry of micro organisms ?

Skin on our body .

Among the options provided, Skin on our body does not primarily act as a physiological barrier to protect the body from the entry of microorganisms.

While the skin does provide a physical barrier against pathogens, preventing their entry to some extent, it is not the primary barrier designed specifically to prevent microbial entry. Acid in the stomach, saliva in the mouth, and tears from the eyes possess specific components (such as enzymes, antimicrobial proteins, and pH levels) that serve as physiological barriers actively aimed at preventing the entry and proliferation of microorganisms.