Question

The endocrine system involves communication by chemical messengers called _____, which circulate through the _____.

Answer 1

Your answers would be Hormones and Bloodstream

hope this helps.  

Answer 2

Answer:

1. "HORMONES"

2. "BLOODSTREAM"

Explanation:

endocrine glands are the ductless glands which secrete chemical messengers called as hormones ,and these circulate through bloodstream to targeted sites where they inhibit or enhance a function occuring.