Final answer:
Tears have limitations as a non-specific defense mechanism, including limited protection scope, inability to target specific pathogens, and potential for overproduction leading to blurred vision. They also contain lysozyme, which is not effective against all pathogens, and their protective function can be decreased by environmental factors.
Step-by-step explanation:
While tears are an important part of the body's innate immune response, they do have some disadvantages as a non-specific defense mechanism. Tears can only provide limited protection; they are effective at washing away pathogens from the eye's surface, but once a pathogen has bypassed this barrier, tears offer no further protection. Additionally, tears lack the sophisticated targeting capabilities of the adaptive immune system and therefore cannot specifically target and destroy pathogens that have entered the body. Moreover, overproduction of tears can lead to blurred vision and may not be sufficient to stave off infections if the pathogen load is particularly high.
Another disadvantage is that while tears contain lysozyme, an enzyme that can break down the cell walls of some bacteria, it is not effective against all types of pathogens, such as certain viruses and resilient bacteria. Furthermore, the continual production of tears and exposure to environmental factors can cause the enzymes and antibodies present in tears to degrade, weakening their protective function. A compromised barrier, whether due to insufficient tear production or excessive dilution of the tear film, can increase susceptibility to infections.