MAJOR ARTERIES and VEINS The aorta is the largest artery in the human body and extends from the heart to the vertebral level of L4 within the abdomen. It supplies all parts of the body excluding the lungs. For descriptive purposes it is subdivided by the thoracic diaphragm into the thoracic aorta and the abdominal aorta. Arteries do not contain valves. Numerous branches arise from the aorta. (a) Thoracic artery • general features: proximal segment of aorta which is located within the thorax; continuous with the abdominal aorta as it passes through the thoracic diaphragm; Examine various torso and head models and identify the following features; • subdivisions of the thoracic aorta: ascending aorta, aortic arch and the descending aorta; • right and left coronary arteries: only branches of the ascending aorta; arise immediately superior to the aortic semilunar valve; supply the heart wall; • aortic arch: continuation of the ascending aorta and begins as the thoracic aorta curves posterolaterally on the left side of the mediastinum; contains 3 collateral branches (from right to left): brachiocephalic trunk, left common carotid artery and left subclavian artery; • brachiocephalic trunk: first branch of the aortic arch; terminally branches into the right subclavian artery and the right common carotid artery (terminally divides into right external and internal carotid arteries); • left common carotid artery: second branch of the aortic arch; terminally branches into left internal and left external carotid arteries in the superior region of the lateral neck; • left subclavian artery: third branch of the aortic arch; supplies structures of the left ______________________________; • posterior intercostal arteries: multiple paired branches of the descending thoracic aorta (only branches of descending part); supply and course through the intercostal spaces of the thoracic wall in the costal grooves of ribs