In computer networks and telecommunications, a dedicated line is a communications connection or other hardware resource dedicated to a certain application or use. This is different than a shared connection such as a telephone network or the Internet.
Carbon dioxide, a waste product of metabolism, travels from the blood to the alveoli, where it can be exhaled. Between the alveoli is a thin layer of cells called the interstitium, which contains blood vessels and cells that help support the alveoli. The lungs are covered by a thin tissue layer called the pleura. The same kind of thin tissue lines the inside of the chest cavity -- also called pleura. A thin layer of fluid acts as a lubricant allowing the lungs to slip smoothly as they expand and contract with each breath.
The alveolar sacs consist of many alveoli and are composed of a single layer of epithelial tissue. There are about 700 million alveoli in the adult lung. The average, healthy adult lungs hold about 13 to 13.5 pints of air (about six liters). The alveoli are considered the functional unit of the lung. In the spaces between the alveoli of the lungs is elastic connective tissue which is important for exhalation. The alveoli are surrounded by a network of pulmonary capillaries.