Mechanics of lungs

06/29/2017
 
The lungs have bronchi that form in a fractal pattern mirroring that of tree branches.
The lungs have bronchi that form in a fractal pattern mirroring that of tree branches.
The surface area of a single human lung is estimated to equal roughly one complete side of a tennis court. Stretching the lung to its ultimate strength would cover an even greater area. The intake of oxygen and expulsion of carbon dioxide happens in little sacs (alveoli) that cover the surfaces of the lungs, which are made up of branches called bronchi. Each lung has about 300 million alveoli, hence the need for surface area.  
 
In a nod to geometry, the bronchi grow in the same type of fractal as tree branches.  A fractal is a repeating pattern in which parts of the whole have the same properties as the whole itself. For example, a triangle made up of other triangles or a tree branch comprised of smaller branches. It is significant that bronchi and tree branches mirror each other because they essentially serve the same respiratory purpose. The concept of similarly functioning things having similar forms is known as the Structure-Function relationship.
 
It is possible to bypass the mouth and nose and breathe directly through the trachea.
It is possible to bypass the mouth and nose and breathe directly through the trachea.
With the amount of working surface area of the lungs, it is important that a disease or problem does not incapacitate the entire lung. To address this, the lungs basically have a built-in factor of safety in the form of independently operating sections. Each section receives its own blood supply, meaning that the failure or removal of one does not necessarily affect the operation of the others. For this reason, lungs are usually able to fully heal from puncture wounds.
 
In contrast, damage from smoke harms the entire lung. When inhaled, smoke can cover the entire surface area just as oxygen does. This is why over time lungs habitually subjected to smoke become darker in color and look shriveled and disjointed compared to healthy lungs.
 
Another factor of safety for the body is the ability to breathe directly through the trachea instead of the mouth or nose. If the airway is blocked due to obstruction, disease, or otherwise unable to function properly, a tracheostomy can be performed.  In this procedure a hole is made in the trachea below the vocal cords. The hole, called a stoma, can be hooked to a ventilator if necessary. A common consequence of this procedure is the inability to speak without artificial assistance. This is because the placement of the stoma allows the airflow to bypass the vocal cords.