The human respiratory system is a series of organs responsible for
taking in oxygen and expelling carbon dioxide. The primary organs of the
respiratory system are lungs, which carry out this exchange of gases as
we breathe.
Red blood cells collect the oxygen from the lungs and carry it to the parts of the body where it is needed, according to the
American Lung Association.
During the process, the red blood cells collect the carbon dioxide and
transport it back to the lungs, where it leaves the body when we exhale.
The human body needs oxygen to sustain itself. A decrease in oxygen is
known as hypoxia and a complete lack of oxygen is known as anoxia and,
according to
MedLine Plus. These conditions can be fatal; after about four minutes without oxygen, brain cells begin dying, according to
NYU Langone Medical Center, which can lead to brain damage and ultimately death.
In humans, the average rate of breathing is dependent upon age. A
newborn's normal breathing rate is about 40 times each minute and may
slow to 20 to 40 times per minute when the baby is sleeping, according
to the
Children's Hospital of Philadelphia.
For adults, the average resting respiratory rate for adults is 12 to 16 breaths per minute, according to
Johns Hopkins Medicine.
Physical exertion also has an effect on respiratory rate, and healthy
adults can average 45 breaths per minute during strenuous exercise.
Parts of the respiratory system
As we breathe, oxygen enters the nose or mouth and passes the sinuses,
which are hollow spaces in the skull. Sinuses help regulate the
temperature and humidity of the air we breathe.
The trachea, also called the windpipe, filters the air that is inhaled,
according to the American Lung Association. It branches into the
bronchi, which are two tubes that carry air into each lung. The
bronchial tubes are lined with tiny hairs called cilia. Cilia move back
and forth, carrying mucus up and out. Mucus, a sticky fluid, collects
dust, germs and other matter that has invaded the lungs. We expel mucus
when we sneeze, cough, spit or swallow.
The bronchial tubes lead to the lobes of the lungs. The right lung has
three lobes; the left lung has two, according to the American Lung
Association. The left lung is smaller to allow room for the heart,
according to the
National Heart, Lung and Blood Institute
(NHLBI). Lobes are filled with small, spongy sacs called alveoli, and
this is where the exchange of oxygen and carbon dioxide occurs.
The alveolar walls are extremely thin (about 0.2 micrometers). These
walls are composed of a single layer of tissues called epithelial cells
and tiny blood vessels called pulmonary capillaries.
Blood passes through the capillaries. The pulmonary artery carries
blood containing carbon dioxide to the air sacs, where the gas moves
from the blood to the air, according to the NHLBI. Oxygenated blood goes
to the heart through the pulmonary vein, and the heart pumps it
throughout the body.
The diaphragm, a dome-shaped muscle at the bottom of the lungs,
controls breathing and separates the chest cavity from the abdominal
cavity, the American Lung Association noted. When a breath it taken, it
flattens out and pulls forward, making more space for the lungs. During
exhalation, the diaphragm expands and forces air out.
Diseases of the respiratory system
Diseases and conditions of the respiratory system fall into two
categories: Viruses such as influenza, bacterial pneumonia and the new
enterovirus respiratory virus
that has been diagnosed in children; and chronic diseases, such as
asthma and chronic obstructive pulmonary disease (COPD). According to
Dr. Neal Chaisson, who practices pulmonary medicine at the
Cleveland Clinic,
there is not much that can be done for viral infections but to let them
run their course. "Antibiotics are not effective in treating viruses
and the best thing to do is just rest," he said.
COPD is the intersection of three related conditions — chronic
bronchitis, chronic asthma and emphysema, Chaisson told Live Science. It
is a progressive disease that makes it increasingly difficult for
sufferers to breath.
Asthma is a chronic inflammation of the lung airways that causes
coughing, wheezing, chest tightness or shortness of breath, according to
Tonya Winders, president of the
Allergy & Asthma Network. These
signs and symptoms may be worse when a person is exposed to their
triggers, which can include air pollution, tobacco smoke, factory fumes,
cleaning solvents, infections, pollens, foods, cold air, exercise,
chemicals and medications.
Lung cancer is often associated with smoking, but the disease can
affect non-smokers as well. Every year, about 16,000 to 24,000 Americans
die of lung cancer, even though they have never smoked, according to
the
American Cancer Society. Like all cancers, lung cancer is caused by the uncontrolled growth of abnormal cells.
Diagnosing and treating respiratory ailments
Pulmonologists, a subspecialty of internal medicine, treat the respiratory system, including the lungs, according to the
American College of Physicians.
Because of the critical nature of the respiratory system,
pulmonologists work in hospitals as well as in private practice. A
pulmonologist must first be certified by the American Board of Internal
Medicine and then obtain additional training in the subspecialty.
Common diagnostic tools for diagnosing respiratory disease include
chest X-rays and a pulmonary function test (PFT), according to
Merck Manuals. A PFT measures how well the lungs take in and release air and how well they circulate oxygen.
A doctor may also perform a
bronchoscopy
by inserting a tube with a light and camera into the airways — the
trachea and the bronchial tubes — to examine for bleeding, tumors,
inflammation or other abnormalities, according to the NHLBI. A similar
procedure is a thoracoscopy, in which a doctor uses an optical device to
examine the surfaces of the lungs.
A physician may order a PFT as part of a routine exam — especially for smokers, according to the
University of Pittsburgh Medical Center. A PFT may also be ordered to test lung function before surgery or to help diagnose lung conditions or diseases.
For most healthy individuals, the most common respiratory ailment they
may face is an infection, according to Dr. Matthew Exline, a
pulmonologist and critical care expert at The Ohio State University
Wexner Medical Center. A cough is the first symptom, possibly
accompanied by a fever.
"However, cough can be a sign of chronic respiratory conditions such as
asthma, chronic bronchitis or emphysema," he said. "In chronic lung
disease, most respiratory diseases present with shortness of breath,
initially with exertion, such as walking a significant distance or
climbing several flights of stairs."
The most certain way to diagnose asthma is with a lung function test, a
medical history and a physical exam, according to Winders. "However,
it's hard to do lung function tests in children younger than 5 years.
Thus, doctors must rely on children's medical histories, signs and
symptoms, and physical exams to make a diagnosis."
For COPD, many patients benefit from respiratory rehabilitation,
according to Dr. Brian Carlin, assistant professor of medicine at
Drexel University College of Medicine.
"It is much like cardiac rehabilitation for heart patients, and can
provide education, exercise and training to reduce the number of
respiratory incidents."
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