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Human Respiratory System
How it works.
The simple task of the
respiratory system is to
supply the blood cells with
oxygen.
When we breathe.
Oxygen cell.
Respiration is
achieved through
the mouth, nose,
trachea, lungs and
diaphragm.
Oxygen then
enters through the
mouth and nose.
Organization of the
Respiratory System
• The respiratory system is divided
into the upper respiratory system,
above the larynx, and the lower
respiratory system, from the larynx
down
Components of the Respiratory System
Figure 23–1
The Respiratory Tract
• Consists of a conducting portion:
• from nasal cavity to terminal
bronchioles
• Consists of a respiratory portion:
• the respiratory bronchioles and alveoli Are air-filled pockets within the lungs
• where all gas exchange takes place
Image of the Respiratory System
Figure 23.3 The Nose, Nasal Cavity, and
Pharynx
Figure 23.3c
Bronchi – the two large passageways that lead from the
trachea to your lungs (one for each lung)
-- the bronchi are further subdivided into bronchioles
-- eventually, the further subdivisions lead to tiny air
sacs called alveoli
-- alveoli are in clusters, like grapes
-- capillaries surrounding each alveolus is where
the exchange of gases with the blood occurs
The diaphragm is the muscle that causes you to breath
-- hiccups are involuntary contractions of the
diaphragm
Figure 23.10 The Bronchi and Lobules of
the Lung
Figure 23.10a
Figure 23.10 The Bronchi and Lobules of
the Lung
Figure 23.10b
Overview
•Respiration = gas exchange - Occurs at the levels of the
lungs and tissues (external
respiration) and cell (internal
or cellular respiration).
•External respiration:
- Pulmonary
ventilation: movement of air in and
out
of the lungs
-Gas exchange in the
alveoli
-Gas transport in the blood
-Gas exchanges between
blood and tissues
Respiratory airway: Alveoli
•Alveolar wall is formed by simple squamous epithelium = type I
cells (SSE)  gas exchange
•Respiratory membrane: membrane separating alveolus from
blood capillary.
•Large surface area from the numerous alveoli  better gas
exchange
•Presence of elastic fibers between alveoli
Airways
•Upper airways:
- nose to pharynx
•Lower airways:
- Conducting airway:
larynx bronchioles
- Respiratory airway:
alveoli
Blood supply to the lungs
Figure 23.2 The Respiratory Epithelium of
the Nasal Cavity and Conducting System
Figure 23.2
The Respiratory Defense System
• Consists of a series of filtration
mechanisms
• Removes particles and pathogens
Components of the Respiratory Defense
System
•Goblet cells and
mucous glands:
•produce mucus that
bathes exposed
surfaces
•Cilia:
•sweep debris
trapped in mucus
toward the pharynx
(mucus escalator)
Components of the Respiratory Defense
System
• Filtration in nasal cavity removes
large particles
• Alveolar macrophages engulf small
particles that reach lungs
The Nose
•Air enters the
respiratory system:
•through nostrils or
external nares
•into nasal vestibule
•Nasal hairs:
•are in nasal
vestibule
•are the first particle
filtration system
The Nasal Cavity
•The nasal septum:
•divides nasal cavity
into left and right
•Mucous secretions
from paranasal sinus
and tears:
•clean and moisten
the nasal cavity
•Superior portion of
nasal cavity is the
olfactory region:
•provides sense of
smell
Air Flow
• From vestibule
to internal
nares:
• through
superior,
middle, and
inferior
conchae
The Palates
• Hard palate:
• forms floor of
nasal cavity
• separates nasal
and oral cavities
• Soft palate:
• extends
posterior to hard
palate
• divides superior
nasopharynx
from lower
pharynx
The Nasal Mucosa
• Warm and
humidify
inhaled air for
arrival at lower
respiratory
organs
• Breathing
through mouth
bypasses this
important step
The Pharynx
• A chamber
shared by
digestive and
respiratory
systems
• Extends from
internal nares to
entrances to
larynx and
esophagus
Divisions of the Pharynx
• Nasopharynx
• Oropharynx
• Laryngopharynx
The Nasopharynx
• Superior portion
of the pharynx
• Contains
pharyngeal
tonsils and
openings to left
and right
auditory tubes
The Oropharynx
• Middle portion of
the pharynx
• Communicates
with oral cavity
The Laryngopharynx
• Inferior portion
of the pharynx
• Extends from
hyoid bone to
entrance to
larynx and
esophagus
Anatomy of the Larynx
Figure 23–4
Cartilages of the Larynx
• 3 large, unpaired
cartilages form the
larynx:
• the thyroid cartilage
• the cricoid cartilage
• the epiglottis
The Thyroid Cartilage
• Also called the
Adam’s apple
• Is a hyaline cartilage
• Forms anterior and
lateral walls of larynx
• Ligaments attach to
hyoid bone, epiglottis,
and laryngeal
cartilages
The Cricoid
Cartilage
• Is a hyaline
cartilage
• Form posterior
portion of larynx
• Ligaments attach
to first tracheal
cartilage
The Epiglottis
• Composed of
elastic
cartilage
• Ligaments
attach to
thyroid
cartilage and
hyoid bone
Cartilage Functions
• Prevents entry of food and liquids into
respiratory tract
• During swallowing:
• the larynx is elevated
• the epiglottis folds back over glottis
• Thyroid and cricoid cartilages support and
protect:
• the glottis
• the entrance to trachea
The Glottis
Figure 23–5
Sound Production
• Air passing through glottis:
• vibrates vocal folds
• produces sound waves
Sound Variation
• Sound is varied by:
• tension on vocal folds
• voluntary muscles
• Speech is done at the larynx
Anatomy of the Trachea
Figure 23–6
The Trachea
• Also called the
windpipe
• Extends from
the cricoid
cartilage into
pulmonary
bronchi
• where it
branches into
right and left
pulmonary
bronchi
The Tracheal Cartilages
• 15–20 tracheal cartilages:
• strengthen and protect airway
• discontinuous where trachea contacts
esophagus
• Ends of each tracheal cartilage are
connected by:
• an elastic ligament and trachealis
muscle
The Primary Bronchi
• Right and left primary bronchi:
• separated by an internal ridge (the carina)
The Right Primary Bronchus
• Is larger in diameter than the left
• Descends at a steeper angle
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The Lungs
• Left and right
lungs:
• are in left and
right pleural
cavities
• The base:
• inferior portion
of each lung
rests on superior
surface of
diaphragm
The Right Lung
• Has 3 lobes:
• superior,
middle, and
inferior
• separated by
horizontal and
oblique
fissures
The Left Lung
• Has 2 lobes:
• superior and
inferior
• are separated
by an oblique
fissure
Relationship between Lungs and Heart
Figure 23–8
• is displaced upward by l
Lung Shape
• Left lung:
• is longer
• is displaced leftward by the heart
forming the cardiac notch
A Primary Bronchus
•Branches to form
secondary bronchi
(lobar bronchi)
Secondary Bronchi
• Branch to form
tertiary bronchi,
also called the
segmental bronchi
Bronchitis
• Inflammation of bronchial walls:
• causes constriction and breathing
difficulty
• Each small
bronchi branches
into multiple
bronchioles
• Bronchioles
branch into
terminal
bronchioles:
• 1 tertiary
bronchus forms
about 6500
terminal
bronchioles
The Bronchioles
Alveolar
Organization
• Respiratory
bronchioles are
connected to
alveoli along
alveolar ducts
• Alveolar ducts
end at alveolar
sacs:
• common
chambers
connected to
many individual
alveoli
An Alveolus
• Has an
extensive
network of
capillaries
• Is
surrounded
by elastic
fibers
Inflammation of Lobules
• Also called pneumonia:
• causes fluid to leak into alveoli
• compromises function of respiratory
membrane
Mechanics of breathing
•Boyle’s law: The
pressure of a gas in a
closed container is
inversely proportional to
the volume of the
container.
•Air flow in the lungs is
driven by the differences
in pressure between the
atmosphere and the
alveoli
•P.atm is constant 
changes in P.alv drive
ventilation
Gas Pressure and Volume
Figure 23–13
Atmospheric Pressure
• The weight of air:
• has several important physiological
effects
Boyle’s Law
• Defines the relationship between gas
pressure and volume:
• As volume decreases, pressure increases
• In a contained gas:
• external pressure forces molecules closer
together
• movement of gas molecules exerts pressure on
container
Mechanisms of Pulmonary Ventilation
Figure 23–14
The Respiratory Muscles
Figure 23–16a, b
The Respiratory Muscles
Figure 23–16c, d
3 Muscle Groups of Inhalation
1. Diaphragm:
•
•
contraction draws air into lungs
75% of normal air movement
2. External intracostal muscles:
•
•
assist inhalation
25% of normal air movement
3. Accessory muscles assist in
elevating ribs:
•
•
•
•
sternocleidomastoid
serratus anterior
pectoralis minor
scalene muscles
Pleura and negative pressure
•Pneumothorax: lung
collapse due to air
entering in the pleural
cavity
Respiratory Disorders: Chronic
Obstructive Pulmonary Disease
(COPD)
 Features of these diseases
 Patients almost always have a history of
smoking
 Labored breathing (dyspnea) becomes
progressively more severe
 Coughing and frequent pulmonary
infections are common
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Chronic Obstructive Pulmonary Disease
(COPD)
Figure 13.13
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Lung Cancer
 Accounts for 1/3 of all cancer deaths in
the United States
 Increased incidence associated with
smoking
 Three common types
 Squamous cell carcinoma
 Adenocarcinoma
 Small cell carcinoma
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Sudden Infant Death syndrome
(SIDS)
 Apparently healthy infant stops
breathing and dies during sleep
 Some cases are thought to be a
problem of the neural respiratory control
center
 One third of cases appear to be due to
heart rhythm abnormalities
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Asthma
 Chronic inflamed hypersensitive
bronchiole passages
 Response to irritants with dyspnea,
coughing, and wheezing
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Asthma
 Chronic inflamed hypersensitive
bronchiole passages
 Response to irritants with dyspnea,
coughing, and wheezing
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
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Developmental Aspects of the
Respiratory System
 Important birth defects
 Cystic fibrosis – oversecretion of thick
mucus clogs the respiratory system
 Cleft palate
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Aging Effects
 Elasticity of lungs decreases
 Vital capacity decreases
 Blood oxygen levels decrease
 Stimulating effects of carbon dioxide
decreases
 More risks of respiratory tract infection
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Respiratory Rate Changes
Throughout Life
 Newborns – 40 to 80 respirations per
minute
 Infants – 30 respirations per minute
 Age 5 – 25 respirations per minute
 Adults – 12 to 18 respirations per
minute
 Rate often increases somewhat with old
age
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
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