Lung Diseases

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Overview of the lungs

The lungs are part of the respiratory (breathing) system and are located in the chest, inside the rib cage and above the diaphragm. Lungs are complex organs that consist of spongy, elastic tissue that is designed to transfer oxygen from the air we breathe into our blood stream and remove carbon dioxide from our blood.

Oxygen in air enters the lungs when we take a breath. It is distributed throughout the lungs by a system called the bronchial tree. It is easiest to imagine the bronchial tree as an upside-down tree starting at our mouth and spreading out across the upper part of our chests. The first tube (airway) is called the trachea or wind pipe. This is similar to the trunk of a tree and guides the oxygen down through our neck from our mouths towards our lungs. The trunk of this tree then splits in two and becomes the left and right bronchus which supplies the left and right lung respectively. These two branches then spread further and as the branches spread out they become thinner until their width is less than 1 mm. These thin branches are called bronchioles.

These brioncholes carry air to small sacs calledalveoli deep within the lungs which are responsible for the exchange of gas between the blood stream and the lungs. In the alveoli oxygen moves from the lungs into the blood stream which is then carried around to supply our body with oxygen. In addition, carbon dioxide, a waste product of our metabolism, moves from the blood into the lungs to be exhaled (blown out) so that we can get rid of it from our body. The mechanics of breathing in oxygen and delivery to tissue in blood is necessary for all of the cells in our body to function. Removal of carbon dioxide is necessary to prevent the body becoming too acidic which could stop the cells in our body from functioning.

The lungs are covered by a thin layer of tissue called the visceral pleura. This layer continues on to the chest wall and around the heart and is called the parietal pleura. There is a thin layer of fluid between these two layers which allows movement between these two layers. The small space between these two layers is called the pleural space. Any increase in this level of fluid between the two layers can cause pressure on the lungs and affect the function of the lungs.

The air we breathe contains many dangerous particles from the environment such as dust, pollens, bacteria, viruses, smoke, and damaging chemicals. Our lungs maintain a system of defence against these potentially toxic invaders. This includes immune cells and secretion of mucus to trap and remove these unwanted substances from the lungs. Every time we cough up sputum we are also coughing up thousands of microscopic particles that could have damaged our lungs.

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