Question

what body system protects against things like chemicals or pathogens freely entering your body and its systems?
integumentary system
immune system
circulatory system
endocrine system
lymphatic system

Explanation:

The integumentary system (skin, hair, nails etc.) forms a physical barrier preventing chemicals and pathogens from entering the body. The immune system defends the body against pathogens that have entered. The circulatory system is for transporting blood and substances. The endocrine system regulates body - functions via hormones. The lymphatic system is part of the immune system but mainly focuses on fluid balance and immunity. The primary barrier against external invaders is the integumentary system.

Answer:

integumentary system