Emphysema

The lungs are two large, spongy sacs that lie on each side of the chest (thorax), separated by the heart. The right lung is divided into three lobes and the left into two lobes. Each lobe is further divided into two to five segments, which are divided by a membrane. Each segment is supplied with incoming air by a branching tube called a bronchiole. The bronchioles are connected to larger and larger bronchioles which in turn connect to large tubes called bronchi (singular: bronchus). The bronchus from each lung merges into a single tube called the trachea, which connects with the upper part of the respiratory system leading to the nose.

The lungs are made up of approximately 300 million tiny air sacs called alveoli (singular: alveolus). Each sac is surrounded by tiny blood vessels, and it is here that the carbon dioxide from the body is exchanged for fresh oxygen that has been inhaled into the lungs.

During respiration, the diaphragm, which forms the floor of the thorax, moves downward toward the abdomen and draws fresh air, inflating the lungs. When the diaphragm relaxes, it resumes its resting domed shape, which forces the air, now heavy with carbon dioxide, out of the lungs. The cycle then is repeated for the next breath. In the case of lung disease such as emphysema the declining number of alveoli means that less oxygen is absorbed into the blood with each breath. At first this may not be a discomfort, especially when the individual is at rest, but with exercise or as more of the alveoli are destroyed the patient will notice an increasing difficulty in getting his breath. He will tire easily and will need to sit down and gasp for air.