Aortic

The aorta carries oxygenated blood to the body and originates at the aortic orifice from the left ventricle of the heart.  From the aorta's point of origin to the arch of the aorta is referred to as the ascending aorta.  The aortic arch begins at the level of the sternal angle and rises anterior to the right pulmonary artery, reaching its highest point to the left of the trachea, and descending posterior to the left root of the lung.  Posterior to the second left sternocostal joint, the aortic arch continues downward as the descending aorta, also called the thoracic aorta.  Once the thoracic aorta passes through the aortic hiatus of the diaphragm on its downward journey, it becomes the abdominal aorta.  The abdominal aorta reaches a termination point just inferior to the umbilicus and slightly to the left of the midsagittal plane as it bifurcates into the left and right common iliac arteries.

The only branches of the ascending aorta are the left and right coronary arteries.  As the aorta continues, there are three branches from the aortic arch.  In order from the most proximal in relation to the ascending aorta, the branches of the aortic arch are the brachiocephalic trunk, the left common carotid, and the left subclavian arteries.  Continuing inferiorly, the thoracic aorta gives rise to four pairs of branches and three unpaired branches.  As the thoracic aorta descends, there are the paired bronchial, posterior intercostal, subcostal, and superior phrenic arteries.  Also found as the thoracic aorta descends are the unpaired mediastinal arteries, esophageal arteries, and pericardial arteries.  The unpaired arteries of the thoracic aorta are not paired with their partner branches, but there are more than one of each of these arteries coming off of the thoracic aorta.  After passing through the aortic hiatus, there are four unpaired branches and five paired branches from the abdominal aorta.  The unpaired branches from most superior to most inferior are the celiac trunk, superior mesenteric artery, inferior mesenteric artery, and the median sacral artery.  Also found along the abdominal aorta's descent are the paired branches of the inferior phrenic, middle suprarenal, renal, ovarian/testicular, and lumbar arteries. 

The branches from the ascending aorta have several significant branches of their own.  From its point of origin, the left coronary artery (LCA) courses between the left auricle and the left side of the pulmonary trunk and through the coronary sulcus where at the superior margin of the anterior IV groove it divides into the anterior IV branch and the circumflex branch.  In some people the anterior IV branch gives off a lateral branch which courses over the anterior surface of the heart.  The branches of the LCA also include a left marginal artery and sometimes the nodal branch to the SA node.  On the other hand, the RCA runs to the right side of the pulmonary trunk through the coronary sulcus and typically gives off a branch to the SA node, the SA nodal branch.  The RCA continues through the coronary sulcus and gives off a second branch, the right marginal branch; a third branch, the atrioventricular nodal branch; and usually gives off the posterior IV branch as well.

The branches of the aortic arch also have their own significant branches.  The brachiocephalic trunk bifurcates into the right common carotid artery and the right subclavian artery.  Dividing in the cervical region at the fourth cervical vertebrae, the left common carotid artery forms the external and internal carotid arteries of the left side.  While not having branches in the mediastinal region, the left subclavian artery does branch outside of this area to give rise to the vertebral artery, internal thoracic artery, thyrocervical trunk, costocervical trunk, and the dorsal scapular artery.  Once the left subclavian artery reaches the lateral border of the first rib it is referred to as the axillary artery.  It is important to note that variation in regards to the circulatory system in some form is far more common than one might expect and should always be considered.  The aortic arch branching pattern of the brachiocephalic trunk, left common carotid, and the left subclavian is referred to as the "Type A" branching pattern.

In regards to the branches of the thoracic aorta, the bronchial arteries generally run along, and branch with, the bronchi to supply the lungs with oxygenated blood.  The subcostal arteries have a posterior branch that is significant, but otherwise the subcostal arteries, posterior intercostal, and superior phrenic arteries give rise to small vessels that are unnamed and serve to distribute successively smaller vessels to supply oxygenated blood to tissue.  The subcostal arteries supply oxygenated blood primarily to the upper, posterior abdominal wall while the posterior intercostal artery branches supply the thoracic wall.  The vessels of the superior phrenic arteries supply the posterior region of the superior surface of the diaphragm.  The mediastinal arteries are once again small vessels that distribute oxygenated blood to tissue, in this case mostly the lymph glands and tissue of the posterior mediastinum.  The esophageal and pericardial arteries supply oxygenated blood through successively smaller vessels to the esophagus and pericardium, respectively.

Several of the branches of the abdominal have their own significant branches.  The celiac trunk has three main branches which are the left gastric artery, the common hepatic artery, and the splenic artery.  The superior mesenteric artery also has several main branches which are the inferior pancreatoduodenal artery, middle colic artery, right colic artery, intestinal arteries, and the ileocolic artery.  Somewhat similar to the superior mesenteric artery in its subsequent branches is the inferior mesenteric artery.  These subsequent branches are the left colic artery, sigmoid branches, and the superior rectal artery.  Of a somewhat lesser divisive status are the inferior phrenic arteries which both divide into a medial and lateral branch and give rise to the superior suprarenal branches.  The renal arteries serve their purpose of supplying the kidneys with oxygenated blood without giving rise to branches for other purposes.  Serving the purpose of sending successively smaller branches to supply oxygenated blood to certain areas without any major branches are the median sacral artery, the middle suprarenal arteries, and the lumbar arteries.

A. Robinson
Sources:

Moore, Dalley, Agur: Clinically Oriented Anatomy. 6th ed. Baltimore:  Lippincott Williams & Wilkins, 2010.

http://www.clevelandclinic.org/heartcenter/pub/guide/heartworks/bloodvesselpics.htm
http://www.imaios.com/en/e-Anatomy/Thorax-Abdomen-Pelvis/Mediastinum-Illustrations
http://www.coryi.org/cardiology/index.htm