Final answer:
Saliva contains lysozyme and immunoglobulin A, which have antibacterial properties and help prevent the penetration of microbes.
Step-by-step explanation:
Saliva contains an antibacterial component called lysozyme, which is an enzyme that can damage the cells of bacteria. Lysozyme is part of the innate immune system and helps prevent microbes from penetrating the epithelium. Additionally, saliva contains immunoglobulin A, which also helps prevent the penetration of microbes.