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.
Aorta, arising from the left ventricle, ascending, arching, then descending through the thorax to the abdomen, where it divides into the common iliac arteries. abdominal aorta the distal part of the descending aorta, below the diaphragm; it is continuous with the thoracic aorta.onsists of four parts: the ascending aorta, the arch of the aorta, the thoracic portion of the descending aorta, and the abdominal portion of the descending aorta. Gives rise to the common carotid and subclavian arteries on the left side and to the brachiocephalic artery on the right side.