It is a portion of the aorta commencing at the upper part of the base of the left ventricle, on a level with the lower border of the third costal cartilage behind the left half of the sternum.
"Human Anatomy - Lab 25 Step 12". Archived from the original on 2016-03-17. Retrieved 2007-10-18. https://web.archive.org/web/20160317160435/http://ect.downstate.edu/courseware/haonline/labs/L25/120100.htm ↩