Final answer:
An open wound represents a "portal of entry" in the chain of infection, as it allows pathogens to enter the body through a break in the skin or mucous membranes.
Step-by-step explanation:
The chain of infection is a sequence that allows pathogens to spread from one host to another. To successfully spread, a pathogen follows several steps, which include finding a source, a means of transmission, a portal of entry, and a susceptible host. An open wound represents a portal of entry in the chain of infection. This is because an open wound is a breach in the protective barriers of the skin and mucous membranes, providing a path for microorganisms to enter the body, also known as the parenteral route. Pathogens need to gain access into host tissue to cause disease, and portals of entry are anatomical sites such as the skin, mucous membranes, and parenteral routes where pathogens can pass into host tissues.