Final answer:
The skin acts as the physical barrier to keep foreign organisms and viruses out of the body.
Step-by-step explanation:
The physical barrier that acts to keep foreign organisms and viruses out of the body is the skin. The skin, which consists of the protein keratin, forms a protective layer that resists physical entry into cells.
Other body surfaces are also protected by mucous membranes that provide a physical trap for pathogens, preventing them from moving deeper into the body.
In addition to the skin and mucous membranes, other mechanical barriers such as the hairs in the nose and the cilia in the upper respiratory tract help to catch and move pathogens out of the body.