Chapter 16 - Respiratory System
Functions of the Respiratory System:
 transport of air into and out of the lungs
 entrapment of particles in incoming air
 help to control temperature and moisture
content of air entering the lungs
 produce vocal sounds
 participate in the sense of smell and in the
regulation of blood pH
Respiration:
The respiratory system consists of tubes that _filter_
incoming air and __transport_ it into the
microscopic alveoli where gases are
_exchanged.
What are the three processes of respiration?
Ventilation, external respiration, internal respiration
Respiratory organs:
The organs of the respiratory tract can be divided
into two groups: the upper respiratory tract
(nose, nasal cavity, sinuses, and pharynx),
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and the lower respiratory tract (larynx,
trachea, bronchial tree, and lungs).
Nose:
The nostrils, openings in the nose, provides an
entrance for air in which air is filtered by
coarse hairs inside the nostrils.
Nasal cavity:
The nasal cavity is a space posterior to the nose that
is divided medially by the _nasal
septum__.
Nasal conchae:
What are they? Bones that curl out from the lateral
walls of the nasal cavity.
What is their function? Divide the nasal cavities into
three passageways and increase surface area to warm
and filter incoming air
The mucus membrane in the conchae secrete a sticky
mucus that traps dust and other small particles
entering with incoming air.
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Cilia:
Particles trapped in the mucus are pushed to the
pharynx by ciliary action, swallowed, and
carried to the stomach_ where gastric
juice destroys any microorganisms in the
mucus.
Paranasal sinuses:
What four bones are they found in? maxillary,
frontal, ethmoid, sphenoid
What is their function? Reduce weight of skull,
serve as resonating chambers for voice quality
Pharynx:
The pharynx is a common passageway for _air_ and
food_ and it aids in producing sounds for
speech_.
Air moves through the larynx, trachea, bronchial tree
into the lungs.
Food moves through the esophagus into the digestive
tract.
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Larynx:
The larynx is an enlargement in the airway superior
to the _trachea__ and inferior to the
_pharynx__.
It helps keep particles from entering the trachea and
also houses the vocal cords.
The larynx is composed of a framework of
_muscles____ and _cartilage___ bound
by elastic tissue.
The three cartilages are the cricoids, epiglottic, and
the thyroid.
The largest cartilage is the thyroid cartilage_(aka
Adam’s apple).
Inside the larynx, two pairs of folds of muscle and
connective tissue covered with mucous
membrane make up the vocal cords.
What are the upper pair called? False vocal cords
(vestibular folds)
What is their function? Help close larynx during
swallowing. This keeps food out of the
airways.
What is the lower pair called? True vocal cords
Their function? Vibrate to produce sounds when air
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is forced between them
What is the triangular slit called where air passes
through? glottis
What closes this space off when swallowing?
epiglottis
Trachea:
The trachea extends downward anterior to the
__esophagus_and into the thoracic cavity,
where it splits into right and left bronchi.
What is the inner wall lined with? Ciliated mucous
membrane
Why? Filters incoming air and moves trapped
particles upwards into the pharynx
The tracheal wall is supported by 20 incomplete
cartilaginous rings.
Why are the rings incomplete rather than complete?
The open area at back permits of expansion of
esophagus when swallowing food
Bronchial tree:
The bronchial tree consists of branched tubes leading
from the _trachea__ to the _alveoli___.
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The bronchial tree begins with the two primary
___bronchi____, each leading to a lung.
Inside the lings the bronchi divide into secondary
bronchi each of which feeds into a lobe
of a lung
How many are on each side? Three on right and two
on left
What are the smallest branches of the bronchial tree
called? bronchioles
Do they have cartilage in their walls? no
Where does the actual gas exchange take place? In
the alveoli
Lungs:
The right and left soft, spongy, cone-shaped lungs are
separated medially by the __mediastinum
and are enclosed by the _diaphragm_ and
thoracic cage.
The bronchus and large blood vessels enter each
lung.
A layer of serous membrane, the visceral _pleura__,
attached to the lung, folds back to form
the __parietal pleura_.
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The __parietal__ pleura lines the thoracic cavity;
serous fluid lubricates the “pleura cavity”
between these two membranes.
Each lobe is composed of lobules that contain air
passages, alveoli, nerves, blood vessels, lymphatic
vessels, and connective tissues
BREATHING:
_ventilation__ (breathing), the movement of air in
and out of the lungs, is composed of 2
processes
called
inspiration_
and
_expiration_.
Inspiration:
__Atmospheric_ pressure is the force that moves air
into the lungs.
As the diaphragm contracts the volume inside the
thoracic cavity increases causing the
pressure in the lungs to decrease.
What happens when pressure on the inside of the
lungs decreases?Air flows in from
outside.
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Air pressure inside the lungs is also decreased by
__increasing the size of the thoracic
cavity; surface tension between the two
layers of pleura causes the lungs follow
with the chest wall and _expand__.
What are the muscles involved in expanding the
thoracic cavity?
diaphragm and
external intercostals
What keeps the alveoli from sticking to each other?
A lipoprotein called surfactant
Lack of surfactant in newborns may cause respiratory
distress syndrome!
Expiration:
The forces of normal expiration are due to the elastic
_recoil_ of lung and muscle tissues and
from the surface tension within the
alveoli.
Forced expiration is aided by __thoracic ___ and
abdominal wall muscles that compress the
abdomen against the diaphragm.
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Respiratory Control:
Normal breathing is a rhythmic, involuntary act
even though the muscles are under
__voluntary___ control.
The respiratory center in __medulla_ & __pons___
impulses to control respiration.
Controlled primarily by levels of __carbon dioxide__
in blood (as CO2 levels increase, breathing rate
increases).
Levels of __oxygen__ play only a minor role, (only
when levels are extremely low).
List three things that affect breathing:
1)Levels of carbon dioxide in the blood,
2) levels of oxygen in the blood and
3) blood pH
An inflation reflex, triggered by stretch receptors in
the visceral pleura, bronchioles, and
alveoli, helps to prevent overinflation of
the lungs during forceful breathing.
Hyperventilation lowers the amount of _carbon
dioxide__ in the blood.
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Gas Exchange:
The __alveoli__ are the only sites of gas exchange
between the atmosphere and the blood.
They are tiny sacs clustered at the distal ends of the
__alveolar ducts.
The ___respiratory__ membrane consists of the
epithelial cells of the alveolus, the
endothelial cells of the capillary, and the
two fused basement membranes of these
layers.
Gases diffuse from areas of __higher___ pressure to
areas of __lower___ pressure.
In a mixture of gases, each gas accounts for a portion
of the total pressure; the amount of
pressure each gas exerts is equal to its
partial pressure.
When the partial pressure of oxygen is higher in the
alveolar air than it is in the capillary
blood, oxygen will diffuse into the
_blood_.
When the partial pressure of carbon dioxide is
greater in the blood than in the alveolar air, carbon
dioxide will diffuse out of the __blood_ and into the
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__alveoli_____.
What factors favor increased diffusion? Increased
surface area, increased partial pressure gradient,
shorter diffusion distance
O2 transport:
Over 98% of oxygen is carried in the blood bound to
_hemoglobin___ of red blood cells,
forming oxyhemoglobin_. This chemical
is unstable in areas where the
concentration of oxygen is low, and gives
up its oxygen molecules in those areas.
More oxygen is released as
1): the blood concentration of carbon dioxide
increases,
2) as the blood becomes more acidic, and
3) as blood temperature increases.
A deficiency of oxygen reaching the tissues is called
hypoxia_and has a variety of causes.
CO2 transport:
Carbon dioxide may be transported in the following
ways:
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1) _dissolved__ in blood plasma,
2) loosely bound to hemoglobin forming
_carbamino hemoglobin__, or
3) as __bicarbonate_ ions.
Which is most common? bicarbonate
When carbon dioxide reacts with water in the plasma,
_carbonic__ acid is formed slowly, but instead much
of the carbon dioxide enters red blood cells, where
the enzyme _carbonic anhydrase__ speeds this
reaction.
The resulting acid dissociates immediately,
releasing bicarbonate and hydrogen ions.
Diseases and Disorders of the Respiratory System
 Asthma –inflammation disorder of airways which
causes wheezing, shortness of breath, chest
tightness, and coughing
 Bronchitis –inflammation of the bronchial linings
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 Cystic fibrosis- a recessive genetic disorder that
causes thick, sticky mucus to build up in the lungs
and digestive tract.
 Emphysema – a progressive degenerative disease
that destroys alveolar walls; this decreases the
surface area of the respiratory membrane and
reduces the volume of gases that can be
exchanged through the membrane. Emphysema
may be developed in response to prolonged
exposure to respiratory irritants like tobacco
smoke and air pollution.
 Pneumonia – infection of the lungs (either viral or
bacterial)
 Lung cancer
 Some lung cancers are secondary cancers,
meaning they arise from cancers elsewhere in
the body that have spread (metastasized) to the
lungs.
 Primary pulmonary cancers begin in the lungs
may arise from epithelial cells, connective
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tissue, or blood; the most common lung cancer,
bronchogenic carcinoma, originates in
epithelial cells and is a response to respiratory
irritants like tobacco smoke. It is possible to be
genetically predisposed to bronchogenic
carcinoma.
Non-respiratory Air Movements
Usually result from reflexes but can be initiated
voluntarily.
 Cough – produces a rapid rush of air against a
closed glottis that removes the irritant from the air
passage.
 Sneeze- a reflex that works similar to a cough but
clears the upper respiratory passageways of
irritants.
 Hiccup- a spasmodic contraction of the diaphragm
while the glottis is closed causes a sudden
inspiration; air striking the vocal cords causes the
sound. The function of a hiccup, if there is one,, is
unknown.
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 Yawn – low blood oxygen concentration triggers
the yawn reflex, prompting a very deep breath that
ventilates more of the alveoli.
 Laughing & Crying – involves taking a deep
breath and releasing it in a series of short
expirations
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