The lungs are a component of the group of tissues in the body known as the respiratory system. The lungs bring fresh air containing oxygen into the body, and breathe out unabsorbed and waste gases. Each cell in a person's body requires oxygen to function; oxygen is absorbed by lung tissue and delivered throughout the body by the bloodstream. The lungs, comprised of multiple types of cells and tissues, continue to work day and night to supply the body with the oxygen it needs.
Lobes
The body's two lungs are divided into sections called lobes. The American Lung Association (ALA) describes how the left lung is divided into two lobes, but the right lung is divided into three lobes. In fact, the right lung is also different from the left lung in terms of size: it is slightly larger than the left lung, which makes space for the heart nestled slightly left-of-center next to the left lung. According to the ALA, each lobe looks like a balloon filled with sponge-like tissue.
Bronchi and Bronchioles
The larger tubes that carry the air into and out of the lung are the bronchi. The bronchi divide and become smaller tubes as they go deeper into the lung; these smaller tubes are called bronchioles. The ALA describes how each bronchial tube is lined with hair-like projections called cilia that move in a wave-like motion to push mucus up and out of the body.
Alveoli
At the end of each small bronchiole are tiny air sacs called alveoli, which the ALA describes as the end destination of air that is breathed in. Alveoli, according to the National Lung Health Education Program, are the "working parts" of the lung and enable the exchange of gases into and out of the body. There are millions of these tiny air sacs throughout the lungs. The walls of the alveoli are very thin tissue that is lined with blood vessels that absorb oxygen. Alveoli act like very tiny balloons, expanding to fill with air, and contracting to expel waste gases.
Blood Vessels
The ALA indicates that blood vessels are critical to the lungs' function. The tiny blood vessels lining the alveolar wall, which directly absorb oxygen from the air, are called capillaries. There are also very large blood vessels: the pulmonary artery is the large blood vessel that brings blood to the lung to be replenished with oxygen; the pulmonary vein is the large blood vessel that takes oxygenated blood back to the heart to be directed to all of the body's tissues.
