in the circulation. When the left ventricle contracts to force blood into the aorta, the aorta expands. This stretching gives the potential energy that will help maintain blood pressure during diastole, as during this time the aorta contracts passively. This Windkessel effect of the great elastic arteries has important biomechanical implications. The elastic recoil helps conserve the energy from the pumping heart and smooth out the pulsatile nature created by the heart. Aortic pressure is highest at the aorta and becomes less pulsatile and lower pressure as blood vessels divide into arteries, arterioles, and capillaries such that flow is slow and smooth for gases and nutrient exchange. Clinical significance Aortic aneurysm – mycotic, bacterial (e.g. syphilis), senile, genetic, associated with valvular heart disease Aortic coarctation – pre-ductal, post-ductal Aortic dissection Aortic stenosis Abdominal aortic aneurysm Aortitis, inflammation of the aorta that can be seen in trauma, infections, and autoimmune disease Atherosclerosis Ehlers–Danlos syndrome Marfan syndrome Trauma, such as traumatic aortic rupture, most often thoracic and distal to the left subclavian artery and often quickly fatal Transposition of the great vessels, see also dextro-Transposition of the great arteries and levo-Transposition of the great arteries Other animals All amniotes have a broadly similar arrangement to that of humans, albeit with a number of individual variations. In fish, however, there are two separate vessels referred to as aortas. The ventral aorta carries de-oxygenated blood from the heart to the gills; part of this vessel forms the ascending aorta in tetrapods (the remainder forms the pulmonary artery). A second, dorsal aorta carries oxygenated blood from the gills to the rest of the body and is homologous with the descending aorta of tetrapods. The two aortas are connected by a number of vessels, one passing through each of the gills. Amphibians also retain the fifth connecting vessel, so that the aorta has two parallel arches. History The word aorta stems from the Late Latin from Classical Greek aortē (), from aeirō, "I lift, raise" () This term was first applied by Aristotle when describing the aorta and describes accurately how it seems to be "suspended" above the heart. The function of the aorta is documented in the Talmud, where it is noted as one of three major vessels entering or leaving the heart, and where perforation is linked to death. References External links Arteries of the thorax Arteries of the abdomen Cardiac anatomy