aorta (a-or'tah)

The main trunk of the systemic arterial system, springing from the left ventricle of the heart, proceeding upward, then to the left, forming an arch around the root of the left lung, then downward, through the diaphragm, to a point opposite the fourth lumbar vertebra, where it divides into the two common iliac arteries, abdominal a. That part of the a. situated below the diaphragm. anterior a. The smaller of the two branches into which the common a. divides in many quadrupeds, ascending a. That portion of the a. which is contained within the cavity of the pericardium, cardiac a. That portion of the vascular system of the embryo which is situated just anterior to the bulb us aortae, giving origin to the aortic arches. common a. That portion of the a. which, in many quadrupeds, extends from its origin at the heart to the point of its division into the anterior and posterior aortae. descending a. That portion of the a. which is situated below the termination of the arch, dorsal a. i. In the embryo, the ve el formed by the union of the two primitive aortae; the representative of the abdominal a. of the fully formed animal. 2. The thoracic a. posterior a. The posterior of.the two branches of the common aorta in many quadrupeds, primitive aortae, primitive subvertebral aortae. Syn.: inferior vertebral arteries. In the embryo, two branches given off from the cardiac a., which pa through the first visceral and unite to form the dorsal a. right a. That division of the aortic bulb in the embryo, which eventually forms the pulmonary artery, systemic a. That division of the vascular apparatus of the embryo which ultimately forms the aorta. thoracic a. That portion of the a. which extends from the lower border of the third dorsal vertebra, on its left side, to the diaphragm. [Gr., aorte, from aeirein, to lift, to carry.]