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 arch of the aorta is the second major anatomical region of the aorta; it curves above the heart between the ascending and descending aorta. All of the blood delivered from the heart to the systemic tissues of the body passes through the aorta, making it the largest artery in the human body.s the aorta extends from the heart, it begins as the ascending aorta before turning 180 degrees towards the bodyâs left side in the aortic arch. From the arch the aorta passes posterior to the heart and descends through the thorax and abdomen as the descending aorta....