The function of the respiratory system is rather simple in concept to bring in oxygen from the atmosphere and get rid of carbon dioxide from the blood. Since oxygen (O2) and carbon dioxide (CO2) are gases, the process of bringing one in and excreting the other is called gas exchange. .....

.Air is inhaled first through the mouth and or nose; aka nasopharynx, were it is filtered, warmed, as well as moisturized. Air then passes the Epiglottis and enters the larynx. The air then passes through the (larynx), voice box and into the trachea. The trachea divides into two branches, the right and left bronchus. The air then passes into the bronchi, then to the bronchiole that branch out like branches of a tree. The branches further divide into the alveolar ducts, and then down to the individual alveoli sacs, where oxygen and carbon dioxide exchange takes place.

Oxygen is necessary for normal metabolism; lack of it leads to death in a few minutes. Carbon dioxide is a waste product of metabolism; if breathing stops, carbon dioxide will quickly accumulate to a toxic level in the blood. Thus our lungs, the
Organs that exchange O2 and CO2 with the atmosphere are vital since their total failure is quickly fatal.

We have two lungs, one in the right side of our chest cage and one in the left (Figure l). Between them is the heart, a midline organ that tilts slightly to the left within the chest cage. (You can feel your heart beating by placing your fingertips under your left breast.) Although gas exchange takes place in the lungs, the respiratory system also includes two other components: the part of the central nervous system that controls our breathing, and the chest bellows.

The part of the nervous system that controls breathing is located in the mid-brain, also known as the brain stem. It is an area more primitive than the area of the brain responsible for thinking and motor movements, known as the brain cortex.
Brain stem control of breathing is automatic and functions whether we think about it or not. However, drugs or some diseases may alter it. A relatively common cause of respiratory depression is an overdose with narcotics or sedatives.