Normal Lung Function

Breathing is taken for granted by most people. It is one part of the process of respiration which provides our bodies with a continuous supply of oxygen. Oxygen is the fuel of life. It keeps us all alive.

Oxygen enters our lungs as part of the air that we breathe. It goes to the blood vessels deep in our lungs and then on to all parts of our body. As our body uses oxygen, it makes a waste product called carbon dioxide. We get rid of carbon dioxide when we breathe out.

The Respiratory System

Lung function

When we breathe in, air flows through the nose or mouth, down the throat, through the voice box, and down the windpipe (trachea). The air then comes to two main large airways (the right and left bronchial tubes). These large airways branch into smaller and smaller airways (bronchioles). Wrapped around the airways are muscles that crisscross each other. We have no control over these muscles, and their exact purpose is not known. Air continues through these small airways until it finally reaches the tiny balloon-like air sacs (alveoli). It is at these air sacs that the oxygen is taken into the blood.

Cleaning of Air and Removal of Mucus

The air that we breathe contains many tiny particles that must be removed before the air reaches the air sacs deep in the lungs. The nose partially cleans the air by trapping dirt particles in its hairs. Located inside the airways are glands that produce a sticky fluid called mucus. Mucus coats the airways and traps dirt and germs found in the airways. Tiny broom-like structures (cilia) clear the dirty mucus from the airways. These sweep the mucus up toward the throat where it can be spit out or swallowed.

Moisturizing the Air We Breathe

If the air we breathe in is too dry, it can damage the tiny air sacs in our lungs. Therefore, the air must be made moist. This is done by absorbing water from the airways. The moisture in the airways comes from food and drink.

The Muscles of Breathing

Lung function

In order to breathe air into our lungs, we rely on several muscles. The diaphragm is the most important muscle. This is a large, dome-shaped muscle located between the chest and the abdomen. When we breathe in, the diaphragm moves down to let air into the lungs. When we breathe out, the diaphragm relaxes and lets air out of the lungs. There are other muscles that can be used in breathing, including the neck and shoulder muscles and the muscles between the ribs.