A healthy person breathes about 10,000 quarts of air every day. This exposes the lungs to a number of hazards in the air, such as dust, dirt, airborne bacteria and fungal spores. These airborne particles can wreak havoc with the entire body. However, your respiratory system has several ways of fighting back, both physical and chemical.
Definition
Most people think that respiration and breathing are the same thing, but this assumption is not quite accurate. Scientists define respiration as the entire process through which oxygen reaches the body's cells and to produce energy. Breathing, one part of this process, is simply the means by which air enters and leaves the lungs.
Process
Air enters and leaves the body through the upper airway consisting of the nose and mouth and travels to and from the lungs via the respiratory tract. When a person breathes through her nose, a filtering process cleans the air before it enters the lungs. Mucus membranes that contain mucus-secreting cells and a layer of fine hairs called cilia line the nasal passages, larynx and trachea. The constantly moving cilia carry inhaled particles trapped by the mucus, which are either swallowed and destroyed by acid in the stomach or coughed out. Occasionally, they linger and cause infection.
Function
Two factors play a role in determining the ease with which a person breathes. Compliance is the ability of the lungs and chest to increase in volume. Essentially, the greater the compliance or elasticity, the less work it takes to expand the chest and lungs. The other factor is resistance, referring to how easy or difficult it is for air to flow into and out of the lungs. In other words, is there a clear path for the air to follow? The higher the resistance, the more work it takes to inhale and exhale or essentially to breathe. Resistance depends on the diameter of the airways and the presence or absence of obstructions such as mucus or fluid.
Cause
Breathing problems not caused by disease can also disrupt breathing. Although a person can consciously alter his breathing, it is usually an unconscious process controlled by nerve centers in the lower part of the brain stem. Various parts of the body send these nerve centers information about carbon dioxide and oxygen levels in the blood. Physical activity, emotional state and the actual breathing process dictate these levels, as well. These nerve centers then adjust the breathing process accordingly. Injury, exercise, trauma--both physical and mental--medication, body temperature and cigarette smoking can all cause breathing problems.
Effects
Increased airway resistance is a more common breathing problem than reduced compliance. For instance, when a person has asthma, mucus builds up in the airway, causing a blockage of sorts, which interferes with the flow of air. The person has to work harder to move the air in and out of the lungs to get past the mucus. Together, compliance and resistance determine how much energy it takes to breathe. Several diseases can affect compliance and resistance, such as pulmonary fibrosis, emphysema, chronic obstructive pulmonary disease, chronic bronchitis and asthma.
