Answer:
d. all of these are correct
Explanation:
Physical barriers are the first line of defense against invading agents. Examples of physical barriers include intact epithelia, the normal microbiota residing in these epithelia, and normal mucosal self-cleaning processes such as coughing, sneezing, mucus production, gastric acidity, vomiting, diarrhea, and urinary flow. All of these processes together make up a very efficient line of defense.
We can mention some members of the body's first line of defense, they are:
- Skin: It is the main barrier that the body has against pathogens.
- Skin Oil and Sweat Glandulas: It has fatty acids that help the skin to prevent fungus from entering the skin.
- Mucus: It is a fluid produced by the body that has the function of preventing microorganisms from entering the respiratory system, for example.
- Saliva: It has a substance that maintains the lubrication of the mouth and helps protect against viruses that can invade the organs of the respiratory and digestive system.
- Digestive Enzymes: They act on the digestion of food and prevent the proliferation of microorganisms.
- Cilia lining the respiratory tract: Protect the respiratory tract against the entry of microorganisms and invasive substances.
