In the United States, the carriers have effectively exited the tower business. Most sold their towers to companies like American Tower (AMT) and Crown Castle. These companies construct, maintain and operate the towers, and lease space to the carriers. Tower operators such as AMT actively seek to lease the same tower to multiple carriers, and this is a key metric of their financial success. A best-in-class tower operator will have 2-3 carrier tenants per tower.
The descending aorta is the part of the aorta beginning at the aortic arch that runs down through the chest and abdomen. The descending aorta anatomically consists of two portions or segments, the thoracic and the abdominal aorta, in correspondence with the two great cavities of the trunk in which it is situated.
The abdominal aorta is the portion that is located in the abdominal area between the renal arteries and the iliac bifurcation (split) and it travels down the frontal surface of the vertebral column (spine).he aorta is the main trunk of the arterial system that carries oxygenated blood from the heart to all points in the body. The aorta arises from the left ventricle of the heart and ends at the lumbar area where it divides to form the right and left common iliac arteries that run down each leg.