Final answer:
The first part of the aorta as it exits the heart is the ascending aorta. It arises from the left ventricle, extends superiorly, and serves as the key passage for blood to reach the significant branches that supply the upper body.
Step-by-step explanation:
The aorta is the largest artery in the human body, originating from the left ventricle of the heart. It is comprised of several distinct regions, with the initial segment being the ascending aorta. This part moves superiorly from the heart for about 5 cm and terminates at the sternal angle.
Following the ascending aorta, blood flows into the aortic arch, which then transitions into the descending aorta, subdivided into the thoracic aorta and the abdominal aorta. The ascending aorta is crucial for distributing oxygen-rich blood to major arteries that branch off to supply the head, neck, and arms with blood.