It’s easy to overlook your lungs. They are part of the body’s autonomic system. What does that mean? Although you have to think about raising your arm, do you have to will your heart to beat or food to digest? Of course not. These bodily processes operate independently of our conscious thoughts – thank goodness.
A typical adult breathes in and out 12 to 20 times per minute, 60 minutes every hour, 24 hours every day. That works out to 17,280 to 38,800 inhalations and exhalations on a daily basis. Way to go, lungs!
In broad terms, the lungs are responsible for “gas exchange” – the intaking of oxygen and the expulsion of carbon dioxide. But let’s not get ahead of ourselves. Here’s how human lungs work:
When you inhale, the lungs expand and contract like bellows – a device used to blow or pump air. The lungs extract vital oxygen from the inhaled air and pass it on to the rest of the body’s cells. It doesn’t take long for life without oxygen to become quite unpleasant, even deathly:
- Between 30-180 seconds of oxygen deprivation, you may lose consciousness.
- At the one-minute mark, brain cells begin dying.
- At three minutes, neurons suffer more extensive damage, and lasting brain damage becomes more likely.
- At five minutes, death becomes imminent.
- At 10 minutes, even if the brain remains alive, a coma and lasting brain damage are almost inevitable.
- At 15 minutes, survival becomes nearly impossible.
The lungs are remarkably efficient. They are never idle. Once they have removed the oxygen from inhaled air, they push out a waste product called carbon dioxide (CO2 for all you chemistry buffs).
Most of us understand that the act of breathing begins by taking in air through the nose and/or mouth. From there, the air passes down the back of your throat and into the windpipe (trachea, for all you medical buffs). The trachea then splits into bronchial tubes (air passages).
The bronchial tubes also divide into even smaller airways termed bronchioles [bron-kee-OH-leez] which terminate in tiny air sacs (alveoli) that resemble itsy-bitsy balloons. It might astonish you to know that the human body has over 300 million alveoli.
Surrounding the alveoli is a fine net or mesh of tiny blood vessels – the capillaries. At this point, the oxygen from the inhaled air travels through the alveoli walls and into the blood.
Oxygen-enriched blood exits the lungs and travels to the heart which pumps it throughout the body, providing life-giving oxygen to all the cells of every organ and tissue that makes you you.
After the cells have processed the available oxygen, they produce carbon dioxide which is absorbed by the blood. The CO2-laden blood goes back to the lungs and is expelled when you exhale.
The air we breathe contains not only oxygen but unwanted hitch-hikers such as dust, soot, mold, fungi, bacteria, and viruses. Our resilient lungs have natural defense mechanisms to protect us from these unwanted intruders.
For example, only the finest particles – less than 3-5 microns (0.000118 to 0.000196 inches for all you math buffs) – can penetrate into the deep lung.
Furthermore, the body’s air passages are lined with tiny, hard-working hair-like projections called cilia (SILL-ee-ya). It is the cilia that push a liquid layer of mucus to cover and protect the airways.
Mucus (commonly called snot) is nothing to sneeze about. The viscous mucal layer works like a glue trap does for insects or mice, capturing disease-causing pathogens and other infectious microorganisms before they can travel to the lungs.
Those hard-working cilia beat more than 1,000 times per minute. They push the mucus lining the trachea upwards, defying gravity, at a rate of about 0.197 to 0.4 inch per minute. Trapped pathogens and other irritating particles are thus coughed up and out of the body or move into the mouth and swallowed.
The lungs have one more defensive ace up their sleeves – so to speak. The alveolar surfaces are coated with a type of white blood cell called macrophages. These incredible cells actually eat bacteria and other foreign cells. They also help T cells (white blood cells that are involved in acquired immunity) recognize microorganisms that don’t belong in the body, called antigens.
There are three types of T cells:
- Killer T cells identify and latch on to antigens on infected or otherwise abnormal cells, including cancerous cells. True to their name, killer T cells murder harmful cells by piercing the cell membrane and injecting lethal enzymes. Buh-bye now.
- Helper T cells assist other immune cells. Some trigger killer T cells into action, activate macrophages, or help B cells create antibodies which neutralize foreign antigens.
- Suppressor T cells manufacture substances that either help prevent negative cellular responses or regulate and end the immune response.
It takes all of these remarkable bits and pieces of human anatomy to fill our bodies with the oxygen we need to go about our daily business. Now that’s something to bellow about!
Hopefully, at this point, you will never take your lungs for granted again. These vital autonomic organs work ceaselessly, day and night, awake or asleep, to stay alive. The secret to longevity is easy: keep breathing!