Respiratory System
(A) RESPIRATORY SYSTEM
 The respiratory system involves both
external and internal respiration
 External respiration: the exchange of gases
between the atmosphere and the blood
 Internal respiration: the exchange of gases
between the blood and the cells of the body
 Cellular respiration: involves the use of
oxygen to break down glucose in the cell
**The main job of the respiratory system is to
get oxygen into the body and waste gases out
of the body**
 The respiratory system is responsible for
transporting gases to and from the circulatory
system.
 Respiration is a vital function for all living things.
Organisms cannot live more than a few minutes
without oxygen.
 The respiratory system is a group of organs
working together to bring about the exchange of
oxygen and carbon dioxide with the environment.
(B) THE PATH OF AIR
 The human respiratory
system consists of:
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The nose
Pharynx
Larynx
Trachea
Smaller passageways
Lungs
Alveoli
 The path of air is as follows:
 Nose: the air enters through the nose—hairs in the
nose filter dust and particles out of the air
 From the nose, air passes through the pharynx: a
muscular tube that serves as a passageway for both
air and food—when food is swallowed, a flap of
cartilage called the epiglottis, presses down and
covers the opening to the air passage
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From the pharynx, the air moves through the
larynx: the voice box located at the upper end of
the neck
From the larynx, the air passes into the trachea:
another tube—the windpipe—that leads straight
into the chest cavity
The trachea, divides into two smaller tubes, the
bronchi: which lead to the lungs

Within the lung, the bronchi divide into smaller
tubes called bronchioles: continue to subdivide
until they finally end in clusters of tiny hollow air
sacs called alveoli

Alveoli: this is the site of all gas exchange in the
lungs—look like a bunch of grapes
 The lungs are amongst
the largest organs of
the body
 Below the lungs is the
diaphragm—powerful
muscle that spans the
rib cage under the
lungs and aids in
respiration
C) BREATHING
– Breathing: the entrance and exit of air into and
from the lungs
– Ventilation: the term for the movement of air to
and from the alveoli
– Every time you take a breath, or move air in
and out of your lungs, TWO major actions take
place:
 Inhalation: aka INSPIRATION—occurs when air is
pulled into the lungs
 Exhalation: aka expiration—occurs when air is
pulled out of the lungs
 These two actions deliver oxygen to the
alveoli and remove carbon dioxide
 The continuous cycles of inhalation as
exhalation are known as breathing
 These two actions are produced by
movements of the diaphragm
 During INHALATION—the diaphragm is
curved upward—the diaphragm contracts
and moves down causing the volume of the
chest to INCREASE
 During EXHALATION—the diaphragm
relaxes and returns to its curved position—
this causes the air pressure in the chest to
DECREASE—which causes the air in the
lungs to be EXHALED
D) GAS EXCHANGE

Three important things happen to the air
we inhale:
– Oxygen is removed
– Carbon dioxide is added
– Water vapor is added


This occurs in the alveoli in the lungs
Our lungs consist of nearly 300 million
alveoli!!!
 Each alveolus is covered
with capillaries for gas
exchange
 The blood entering the
alveoli contains a large
amount of carbon dioxide
 The blood leaving the
alveoli has nearly tripled
the total amount of oxygen
it originally carried
E) REGULATION OF BREATHING
 Breathing is such an important function that your
nervous system will not let you have complete
control of it.
 Breathing is an involuntary action. This means
that you cannot control it.
 You can hold your breath until you lose
consciousness, but then the brain takes control
and normal breathing resumes
F) Disorders
Lung Disorder
Description
Asthma
Irritated pathways and bronchioles
constrict
Bronchitis
Pathways become infected
Emphysema
Alveoli are destroyed  leads to
trouble breathing and gas
exchange
Pneumonia
Infection of lungs which makes
alveoli produce mucus
Pulmonary Tuberculosis
Lung infection that reduces gas
exchange
Lung Cancer
Uncontrolled growth of lung tissue