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

Your answers would be Hormones and Bloodstream

hope this helps.  

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.

answer: "circumcision is a common procedure in which the skin covering the tip of the penis is surgically removed."

the relative atomic mass of an element is the mass of one atom of that element, relative to 1/12th of the mass of a  1212c atom. to convert to an absolute mass in kg, it is necessary to multiply by  1.661×10−271.661×10−27.

the relative atomic mass is roughly equal to the number of neutrons, plus the number of protons, in the nucleus of the atom.

for elements with more than one stable isotope (different types of nucleus with different numbers of neutrons but the same number of protons), the quoted mass is usually the average mass, weighted by the relative abundance of the different isotopes.