Question

Which acts as both a physical and chemical barrier against pathogens?

blood

skin

lymph

mucus

Answer 1

Skin uniquely acts as both a physical and chemical barrier against pathogens by having a tough protective layer that prevents entry and producing chemicals that hinder microbial growth.

Step-by-step explanation:

The component of the body that acts as both a physical and chemical barrier against pathogens is skin. The skin serves as a mechanical barrier, preventing the physical entry of pathogens through its tough surface layer containing keratin. Additionally, skin produces chemicals such as antimicrobial peptides, with sebaceous glands secreting an acidic film that hinders microbial growth. This dual action makes it an integral part of the body's first line of defense in its immune system.

While other substances like blood, lymph, and mucus play roles in defending the body against invaders, they do not function as both physical and chemical barriers simultaneously. Mucus, for example, does trap pathogens physically, but it is primarily known for its chemical defense with enzymes such as lysozyme that destroy these invaders. Therefore, out of the options provided, skin uniquely fulfills both roles.

Answer 2

Skin

The first line of defense against any pathogen attempting to invade the body is your skin. The largest organ of your body can physically prevent invaders from getting inside and can also chemically change them by methods such as sweat and desiccation.