Question

fill in the blanks below.
the complement system is a \boxed{} barrier of the immune system.
the complement system is a group of \boxed{} in the blood that detect pathogens that have entered the body.
the complement system can cause \boxed{}, the swelling of a part of the body accompanied by redness, swelling, and pain as a response to infection.

Explanation:

1. The complement system is part of the innate immune system, acting as a second (or "humoral" is also accurate, but "second" fits the typical description of immune barriers where the first is physical/chemical, second is innate like complement) barrier. However, more accurately, the complement system is a humoral or a component of the innate immune barrier, but the standard fill - in here (for basic biology) often uses "second" or "humoral", but the most precise in terms of immune barrier classification: the complement system is a humoral (or "second") barrier. But the more accurate term for the first blank: The complement system is a humoral (or in some curricula, "second") barrier of the immune system.
2. The complement system is a group of proteins in the blood that detect pathogens that have entered the body. These are plasma proteins that work in a cascade to help eliminate pathogens.
3. The complement system can cause inflammation, which is defined as the swelling of a part of the body accompanied by redness, swelling, and pain as a response to infection. Inflammation is a key part of the immune response, and the complement system can trigger it.

Answer:

1. The complement system is a \boxed{humoral (or second)} barrier of the immune system. (Note: If "second" is preferred in the curriculum, use that. "Humoral" is more accurate as it's part of the humoral innate immunity. )
2. The complement system is a group of \boxed{proteins} in the blood that detect pathogens that have entered the body.
3. The complement system can cause \boxed{inflammation}, the swelling of a part of the body accompanied by redness, swelling, and pain as a response to infection.