Which of the following is a barrier against pathogens provided by the skin?

low pH

mucus

tears

cilia

Low pH

Explanation:

The skin has sebaceous glands that secrete sebum. Sebum makes a protective layer over the surface of the skin and imparts it an acidic pH due to the presence of fatty acids in it.

Mostly, the pH level of skin is maintained within the range of 3-5 (acidic) which in turn serves as one of the barriers against pathogen provided by skin. Likewise, sweat glands of skin secrete sweat which also imparts the acidic pH to the skin to prevent any infection.