The aorta originates from the left ventricle of the heart. It ends in the abdomen where it branches into the two common iliac arteries. The aorta has five separate segments. The descending aorta begins at the arch of the aorta (where it loops over the heart to begin its descent). It is divided into two segments, the thoracic and the abdominal. The descending aorta (thoracic aorta) is between the arch of the aorta and the diaphragm muscle below the ribs. At the origination point, it is on the left side of the vertebrae. As it descends, it winds around the vertebrae and ends in front. The diameter of the artery is 2.32 centimeters. It has six paired branches: bronchial arteries, mediastinal arteries, esophageal arteries, pericardial arteries, superior phrenic artery, and intercostal arteries. There are nine pairs of the intercostal arteries. The right branches are longer than the left, because the descending aorta (thoracic aorta) is on the left side of the vertebrae. Through its various branches, it supplies blood to the esophagus, lungs, and the chest area, including the ribs and mammary glands.