C. Physiological barriers

- Saliva in the mouth and tears from the eyes are examples of physiological barriers under innate immunity.
- Innate immunity is the first line of defense against pathogens and it provides immediate, non-specific protection.
- Physiological barriers are part of this innate immunity and include various secretions and fluids in the body that help in preventing the entry and spread of pathogens.
- Saliva and tears are two such examples of physiological barriers.

Saliva as a physiological barrier:
- Saliva is produced by the salivary glands in the mouth and it plays a crucial role in maintaining oral health and preventing the entry of pathogens.
- It contains enzymes like lysozyme which can break down the cell walls of certain bacteria, preventing their growth and proliferation.
- Saliva also contains antimicrobial proteins and antibodies that can neutralize viruses and bacteria.
- Additionally, the continuous flow of saliva helps in washing away harmful microorganisms from the surfaces of the teeth and gums.

Tears as a physiological barrier:
- Tears are produced by the lacrimal glands in the eyes and they serve multiple functions, including lubrication and protection of the eyes.
- Tears contain lysozyme, which has antimicrobial properties and can inhibit the growth of certain bacteria.
- They also contain other antimicrobial proteins and antibodies that can help in preventing and fighting infections.
- The flow of tears helps in flushing out any foreign particles or microorganisms that may come in contact with the eyes.

Importance of physiological barriers:
- Physiological barriers like saliva and tears act as the first line of defense against pathogens that try to enter the body through the mouth or eyes.
- They provide a protective layer and help in preventing the colonization and infection by harmful microorganisms.
- These barriers work in combination with other innate immune responses like inflammation and phagocytosis to provide comprehensive protection against pathogens.

In conclusion, saliva in the mouth and tears from the eyes belong to the category of physiological barriers under innate immunity. They play a crucial role in preventing the entry and spread of pathogens, and contribute to the overall defense mechanism of the body.