The physical lines of defense in the human body primarily include skin, cilia, and mucous membranes. These components work together to protect against pathogens and foreign substances.
So, the correct answer is:
- Skin, cilia, and mucous membranes.
Hair, nails, and teeth also play protective roles, but they are not typically categorized as the primary physical barriers in the same way as skin, cilia, and mucous membranes.