on one's shoulders
As one's responsibility, as in The king carries his entire country on his shoulders, or The success of the conference rests on Nancy's shoulders. This metaphoric use of shoulders as the burden-bearing part of the body dates from the late 1300s.
The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.