Learning guide
Respiration means breathing. In this lesson you will learn about
the respiratory
tract, also called the respiratory system. This is the passage
that air goes through as
we breathe in and out. The respiratory tract contains these
important parts:
The upper respiratory tract
→Nose—warms
the air breathed and filters out bacteria and debris. Nasal breathing is
important for best lung function.
→Sinuses—cavities
(holes) in the skull. They connect to the nasal passage and are lined with
nasal tissue.
↓
Pharynx—passageway that conducts air from the nose to the voice box. The
pharynx also conducts food from the mouth to the esophagus, the tube that leads
to the stomach.
↓
Epiglottis—flap that covers the entrance to the voice box when we swallow. It
prevents food and liquids from getting into the lungs.
↓
Larynx—the voice box, located between the pharynx and the windpipe (trachea).
↓
Trachea—windpipe. This is the airway connecting the larynx to the tubes leading
to the lungs (bronchi).
The lower respiratory tract
↓
Bronchi—two tubes that lead from the trachea to the lungs. The bronchi divide
into many smaller airways, called bronchioles.
↓
Lungs—pair of large spongy organs that take oxygen out of the air we breathe
and exchange it for carbon dioxide in our blood.
↓
Alveoli—millions of tiny air sacs in the lungs, surrounded by tiny blood
vessels called capillaries. This is where the exchange of oxygen and carbon
dioxide takes place. These sacs look like bunches of grapes.
→Pleura—a
membrane that covers the lungs and helps them move freely.
How the Respiratory System Works
The respiratory tract inhales oxygen into the lungs,
transfers the oxygen to the blood, and exhales carbon dioxide. Breathing is
usually automatic, controlled subconsciously by the respiratory center at the
base of the brain. The brain senses when oxygen levels are too low or carbon dioxide
levels are too high and increases the speed and depth of breathing. Normal respiration
occurs 12–20 times a minute.
All cells in the body need oxygen. They get oxygen when the
body breathes in air that the blood can circulate to all parts of the body.
Breathing is accomplished with the help of the diaphragm, a set of muscles lying
across the bottom of the chest cavity. Oxygen is pulled into the lungs when the
diaphragm contracts. Carbon dioxide is pumped out when the diaphragm relaxes. Air
inhaled through the nose is filtered, moistened and warmed in the nasal passages.
Air goes down the pharynx, into the trachea, through the larynx and into the two
large bronchi. The bronchi branch into smaller airways that conduct the air
into the lungs. The inhaled oxygen diffuses into the blood through the many
capillaries. The blood exchanges carbon dioxide for oxygen. The carbon dioxide
is then exhaled.
Oxygenated blood travels from the lungs through the pulmonary
veins and into the left side of the heart, which pumps the blood to the rest of
the body.
The blood delivers its oxygen to the tissues and picks up
and distributes nutrients and waste products, then returns to the heart and
gets pumped back to the lungs to pick up oxygen and get rid of carbon dioxide.
Elimination of carbon dioxide is just as important as
getting oxygen. A buildup of carbon dioxide leads to headaches, drowsiness, and
even death.
Fast facts:
Chronic Obstructive Pulmonary Disease (COPD) accounts for
more than 100,000 deaths every year. It is the fourth most common cause of
death in the U.S. People with asthma are almost 60% more likely to develop lung
cancer. Each year more than 25,000 people in the U.S. get tuberculosis (TB).
Problems that develop in the respiratory tract
There are many disorders and infections of the respiratory
system. Infections occur more frequently in the respiratory tract than in any
other organ in the body. Examples of upper respiratory infections include the
common cold, sinusitis, and influenza (flu). Lower respiratory problems include
infections such as bronchitis and pneumonia and disorders like emphysema and
asthma. Some of the more serious ones are described in the following pages.
Upper
respiratory infections
Influenza (Flu)
Influenza is a highly contagious infection of the upper
respiratory tract. It is caused by a virus and spreads easily through coughing
and sneezing. Influenza can lead to pneumonia and death and is responsible for epidemics
that occur almost every winter. Flu vaccine can prevent influenza.
Influenza virus is generally passed from person to person by
airborne transmission. However, the virus can live for a short time on objects
such as pens, pencils, keyboards, and telephone receivers. Touching those
objects can transmit the virus.
Symptoms of influenza include high fever, headache,
sneezing, coughing, sore throat, severe aches and pain, and fatigue. The most
common complications of flu are respiratory disorders, especially bronchitis.
Pneumonia is the most serious complication.
Treatment includes bed rest and increased fluids, antiviral drugs,
and medication to relieve aches and fever. Most people recover in a week, but
many flu victims feel exhausted for 3–4 weeks. Getting the annual flu shot,
washing hands frequently, and avoiding contact with infected persons can
prevent influenza.