Asthma A to Z - The Human Respiratory System

The primary function of our respiratory system is to obtain oxygen for use by our body's cells, and to eliminate the carbon dioxide that our cells produce.  

The first step in understanding the respiratory system is to take a look at the various parts. In general, this system includes airways that lead into and out of the lungs, and, of course, the lungs themselves.

Our lungs allow oxygen to enter the body in exchange for its waste product, carbon dioxide. As the oxygen passes through your nose and mouth, it is rapidly warmed and moistened to avoid injury to the delicate lining of your airways.

The nose and airways trap large particles, like dust, pollen, molds, and bacteria, and also chemicals, which could cause serious injury to the lungs. The air is then transported through the trachea and bronchi to smaller airways called bronchioles. These airways have branches like a tree, so that millions of small airways can carry oxygen to the tiny air sacs called alveoli.

The airways have a delicate cellular lining called mucosa, which is coated with a thin layer of mucus. Foreign particles are trapped by the sticky mucus and eventually removed from the airways through the normal cleansing process.

The process is assisted by the movement of tiny "whip-like" structures, called cilia, that move the mucus and trapped foreign particles up toward the mouth and nose where they are coughed and sneezed out or swallowed.

Bundles of muscles surround the airways, and the contraction of these muscles directs the flow of air.

Now that we're familiar with the parts of the respiratory system, let's take a look at the process. We need a continuous supply of oxygen for cellular respiration, and we must get rid of excess carbon dioxide, which is the poisonous waste product created in our cells. Gas exchange is the exchange of oxygen and carbon dioxide between the air and the blood in the lungs. Blood enters the lungs through the pulmonary arteries. It then moves through arterioles and into the alveolar capillaries. Oxygen and carbon dioxide are exchanged between blood and the air. The blood then flows back to the heart through the pulmonary veins.