Mechanics of lungs
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.
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.