Download The Respiratory System

(Students: Bolded, italicized, and underlined sections will be on the exam)
The Respiratory System:
I. Function of the System:
A. To supply the body with oxygen and to eliminate carbon dioxide. The
respiratory system, including the lungs, brings air into the body by breathing.
The oxygen in the air travels from the lungs into the bloodstream where it is
pumped to the cells in all parts of the body. The body’s cells use the oxygen
(O2 ) as fuel and give off carbon dioxide (CO2 ) as a waste gas (a process called
cellular respiration, which produces energy for cells). The carbon dioxide
waste gas is carried by the bloodstream back to the lungs to be eliminated or
exhaled.
II. The Main Parts of the System: Mouth, Nose, Pharynx, Larynx, Trachea, Epiglottis,
Bronchi, Bronchial Tubes, Lungs, Alveoli, and Diaphragm
A. Mouth and Nose: Air (containing about 20% oxygen) enters the respiratory
system through the mouth and the nose. Inhaling should take place in the nose,
where air can be warmed and dust can be filtered by the nose hairs and sinus
cavities.
B. Pharynx, Larynx (voicebox), and Epiglottis: The air then passes through the
pharynx (throat cavity) and then the upper part of the trachea called the
larynx (the voicebox where speech sounds are produced). Both food and air
travel through the pharynx. The epiglottis is a flap of tissue that opens while
breathing, and closes while swallowing (preventing food from entering the
lungs, as it passes through the pharynx).
C. Trachea (Windpipe): Air then enters the trachea which is a tube that enters the
chest cavity. The trachea is a pipe shaped by rings of cartilage.
D. Bronchi: In the chest cavity, the trachea splits into two smaller tubes called
the bronchi (each one is called a bronchus). These carry air into each lung.
E. Bronchial Tubes and the Lung: Each bronchus leads into the lung, and then
divides again forming the bronchial tubes.
F. Bronchioles and Alveoli: The bronchial tubes lead directly into the lungs
where they divide into many smaller tubes called bronchioles. At the end of
each of these tubes are small air sacs called alveoli. Alveoli is where the gas
exchange takes place.
• The average adult's lungs contain about 600 million of these spongy, air-filled
sacs that are surrounded by capillaries.
• Capillaries, which are small blood vessels with thin walls, are wrapped around
these alveoli. The walls are so thin and close to each other that the oxygen in
the air easily seeps through. In this way, oxygen seeps through the capillary
walls into the bloodstream and carbon dioxide wastes already in the
bloodstream, seep out and into the alveoli.
• The carbon dioxide and ‘unused air’ follows the same path out of the lungs
when you exhale.
G. Diaphragm: The diaphragm is a sheet of muscle that separates the chest cavity
from the abdominal cavity.
• The diaphragm's job is to help pump the carbon dioxide out of the lungs and
pull the oxygen into the lungs.
• As the diaphragm contracts and relaxes, breathing takes place.
• When the diaphragm contracts and flattens, the chest expands and (oxygenrich) air is pulled into the lungs.
• When the diaphragm relaxes, the chest collapses and (carbon dioxide-rich) air
in the lungs is forced out.
• The left side of heart receives and pumps oxygen-rich blood from the lungs,
and then to the rest of the body.
The Parts of the Respiratory System:
III. Interaction with Other Systems:
The respiratory system interacts with every system, since it provides every organ
system’s cells with oxygen, and helps to rid the body of carbon dioxide wastes.
Some examples of systems that directly interact with the system include:
• The Circulatory System: The circulatory system transports the oxygen and
carbon dioxide between the body’s cells and the lungs.
• The Excretory System: The lungs get rid of the carbon dioxide wastes, and are
therefore part of the excretory system (responsible for getting rid of body
wastes).
• IV. Some Diseases and Disorders:
• Bronchitis: Infection (usually viral) of the bronchial tubes; chest pain and
difficulty breathing are symptoms.
• Pneumonia: Infection (usually bacterial) of the linings of the lungs; fluid builds
up in the lungs. Sometimes antibiotics may be effective.
• Asthma: Characterized by inflammation of the bronchial tubes. Causes
wheezing, shortness of breath and difficulty exhaling. Often caused by
exposure to allergens, or exercise. Drugs may effectively help to alleviate
and lessen symptoms.
• Emphysema: Characterized by damage of the air sac walls. Causes shortness
of breath, and difficulty exhaling. Often is a result of smoking for many
years. No cure.
• Lung Cancer: An abnormal growth of lung cells. Often caused by long-term
inhalation of pollutants (especially if the victim has smoked cigarettes for
many years). Can lead to death.
• Cystic Fibrosis: Genetic disorder where mucus in the lungs builds up and
cannot be expelled. No cure.