The body's breathing system is known as the respiratory system and is, with the heart and blood supply, probably the most important system in the body. When working properly it provides us with the oxygen we need to survive and removes carbon dioxide we do not need. The human body can go without food for weeks, without water for days - but without oxygen from the air we breathe we cannot last more than a few minutes.



Of all the muscles in the body, the muscles we use to breathe are the only ones over which we have dual control; that is, they can work both automatically and voluntarily. In healthy people, breathing in and out happens automatically but, when necessary, we can also control it. We do this, for example, to avoid inhaling smoke and fumes, when singing, or when swimming under water.

How We Breathe

The respiratory system is made up of the rib cage and intercostal muscles, the diaphragm - a sheet of muscle between the chest and stomach - and the respiratory tract, which comprises the airways and lungs.

When we breathe, the muscles in the thorax that link the ribs contract, pulling the ribs up and out. The diaphragm pulls the chest cavity down, and together these two processes cause the lungs to expand. Cold air is drawn in through the nose where it is warmed and then taken down into the lungs. When enough air has been inhaled successfully (which is called inspiration), the muscles and diaphragm relax and the air is exhaled as the lungs compress (called expiration). Then the diaphragm contracts once more and the cycle begins again.

When the air passes through the nose it enters the trachea (the windpipe) and the bronchi, Which are small airways that run through each lung.These bronchi become smaller and smaller, eventually taking the form of bronchioles, which end as tiny air sacs called alveoli. The alveoli are linked to blood capillaries, which exchange oxygen and carbon dioxide at a very quick rate.

On average we take about 12 breaths per minute, and that rate is controlled by the body according to its needs at a particular point in time. If there is too carbon dioxide and too little oxygen, the rate of respiration will increase and the body will gulp or gasp for air. This may, for example, occur during strenuous exercise, an asthma attack, or in fright. When the levels of oxygen and carbon dioxide return to normal, breathing returns to its normal rate of respiration.

When we are stressed, we may breathe at an accelerated rate. Rapid breathing is a general response to stress, and it leads to overall tension of the muscles and eventually dizziness, faintness, and a sensation of pins and needles caused by metabolic changes in the body. Overbreathing causes the concentration of carbon dioxide in the alveoli of the lungs to fall, leading to a buildup of alkali in the bloodstream and tissue fluid. This alkalosis produces the symptoms outlined above.

When we breathe normally, and efficiently, we use our diaphragm, which contracts and becomes flat, increasing the space in the chest into which the lungs can expand. When lungs are able to expand to their full capacity, all residual carbon dioxide is expelled and more oxygen can be inhaled. Many adults have to relearn breathing because of lifelong bad habits.

A variety of disorders - physical injury, infections, viruses, allergies, and diseases - can disrupt and endanger the normal breathing processes.