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 Aorta is ARTERY that carries BLOOD from the HEART to the body. 1  The largest blood vessel in the body, the aorta arises from the left ventricle. At its widest point the aorta is about one and a half inches in diameter. As the aorta leaves the heart it ascends to curve behind the right atrium. The first arteries to branch from the base of the ascending aorta are the right and left CORONARY ARTERIES that supply the heart MUSCLE with blood. Branching from the arch as the aorta crests over the heart are the three arteries that carry blood to the upper body: