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Chapter 10
Lecture Outline
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Respiratory System
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Points to ponder
• What are the parts and functions of the upper
and lower respiratory system?
• What is the mechanism for expiration and
inspiration?
• How is breathing controlled by the nervous
system and through chemicals?
• Where and how is exchange of gases
accomplished?
• What are some common respiratory infections
and disorders?
• What do you know about tobacco and health?
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10.1 The Respiratory System
Overview of the respiratory system
Nasal cavity
filters, warms, and moistens air
Pharynx
passage way where pathway
for air and food cross
Upper
Respiratory
Tract
Glottis
space between the vocal chords;
opening to larynx
Larynx
(voice box) ; produces sound
Trachea
(wind pipe) ; passage of air
to bronchi
Bronchus
passage of air to lungs
Lower
Respiratory
Tract
Bronchioles
passage of air to alveoli
Lung
contains alveoli (air sacs);
carries out gas exchange
Diaphragm
skeletal muscle; functions
in ventilation
Figure 10.1 The human respiratory tract.
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10.1 The Respiratory System
What is the pathway that air follows?
nose
pharynx
larynx
trachea
bronchus
bronchioles
alveoli
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10.2 The Upper Respiratory Tract
What constitutes the upper respiratory
tract?
• Nose
sinus
nasal cavity
• Pharynx
hard
palate
nares
sinus
tonsil
Pharynx
nasopharynx
uvula
mouth
• Larynx
tongue
oropharynx
tonsils
epiglottis
glottis
larynx
laryngopharynx
esophagus
trachea
Figure 10.2 The upper respiratory tract.
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10.2 The Upper Respiratory Tract
The nose
• The nose opens at the nostrils/nares and leads
into the nasal cavities.
• Hairs and mucus in the nose filter the air.
• The nasal cavity has a lot of capillaries that warm
and moisten the air.
• Specialized cells act as odor receptors.
• Tear glands drain into the nasal cavities that can
lead to a runny nose.
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10.2 The Upper Respiratory Tract
The pharynx
• The pharynx is a funnel-shaped cavity commonly
called the throat.
• It has three portions based on location:
nasopharynx, oropharynx, and laryngopharynx.
• Tonsils provide a lymphatic defense during
breathing at the junction of the oral cavity and
pharynx.
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10.2 The Upper Respiratory Tract
The larynx
• The larynx is a triangular, cartilaginous
structure that passes air between the pharynx
and trachea.
• It is called the voice box and houses vocal
cords.
• There are two mucosal folds that make up the
vocal cords with an opening in the middle
called the glottis.
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10.2 The Upper Respiratory Tract
The larynx
base of
tongue
epiglottis
vocal
cords
glottis
(left): © CNRI Phototake
Figure 10.4 The vocal cords.
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10.3 The Lower Respiratory Tract
What constitutes the lower respiratory
tract?
• Trachea
Nasal cavity
filters, warms, and moistens air
Pharynx
passage way where pathway
for air and food cross
Upper
Respiratory
Tract
• Bronchial
tree
Glottis
space between the vocal chords;
opening to larynx
Larynx
(voice box) ; produces sound
Trachea
(wind pipe) ; passage of air
to bronchi
Bronchus
passage of air to lungs
• Lungs
Lower
Respiratory
Tract
Bronchioles
passage of air to alveoli
Lung
contains alveoli (air sacs);
carries out gas exchange
Diaphragm
skeletal muscle; functions
in ventilation
Figure 10.1 The human respiratory tract.
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10.3 The Lower Respiratory Tract
The trachea
• The trachea is a tube, often called the
windpipe, that connects the larynx with the
primary bronchi.
• It is made of connective tissue, smooth
muscle, and cartilaginous rings.
• The trachea is lined with cilia and mucus that
help to keep the lungs clean.
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10.3 The Lower Respiratory Tract
The trachea
cilia
goblet cell
epithelial
cell
particle
movement
mucus
air
tracheal
lumen
(bottom half): © ED Reschke
Figure 10.5 The cells lining the trachea.
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10.3 The Lower Respiratory Tract
The bronchial tree
• The bronchial tree starts with two main
bronchi that lead from the trachea into the
lungs.
• The bronchi continue to branch until they
are small bronchioles about 1 mm in
diameter with thinner walls.
• Bronchioles eventually lead to elongated
sacs called alveoli.
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10.3 The Lower Respiratory Tract
The lungs
• The secondary bronchi, bronchioles, and
alveoli make up the lungs.
• The right lung has three lobes while the left
lung has two lobes.
• Each lobe is divided into lobules.
• Each lung is enclosed by membranes called
pleura.
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10.3 The Lower Respiratory Tract
The alveoli
• There are 300 million alveoli in the lungs that
greatly increase surface area.
• Alveoli are enveloped by blood capillaries.
• The alveoli and capillaries are one layer of
epithelium to allow exchange of gases.
• Alveoli are lined with surfactant that act as a
film to keep alveoli open.
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10.3 The Lower Respiratory Tract
The alveoli
pulmonary
vein
blood flow
pulmonary
artery
blood flow
Pulmonary arteriole
contains much CO2, little O2.
bronchiole
Pulmonary venule
contains much O2,
little CO2
lobule
capillary
network
alveoli
Figure 10.6 Pulmonary circulation to and from the lungs.
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10.4 Mechanism of Breathing
Two phases of
breathing/ventilation
1. Inspiration – an active process of inhalation
that brings air into the lungs
2. Expiration – a typically passive process of
exhalation that expels air from the lungs
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10.4 Mechanism of Breathing
Boyle’s Law
• Ventilation is
governed by Boyle’s
Law.
• At a constant
temperature the
pressure of a given
quantity of gas is
inversely proportional
to its volume.
Figure 10.7 The relationship between air pressure
and volume.
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10.4 Mechanism of Breathing
Inspiration
• The diaphragm and intercostal muscles contract.
• The diaphragm flattens and the rib cage moves
upward and outward.
• Volume of the thoracic cavity and lungs increase.
• The air pressure within the lungs decreases.
• Air flows into the lungs.
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10.4 Mechanism of Breathing
Inspiration
trachea
Rib cage
moves
up and out.
External intercostal
muscles
pull the ribs outward.
lungs
Diaphragm
contracts
and moves down.
air in
lung
rib cage
When
Pressure
in lungs
decreases,
air comes
rushing in.
a. Inspiration
Figure 10.8a The thoracic cavity during inspiration.
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10.4 Mechanism of Breathing
Expiration
• The diaphragm and intercostal muscles relax.
• The diaphragm moves upward and becomes
dome-shaped.
• The rib cage moves downward and inward.
• Volume of the thoracic cavity and lungs decreases.
• The air pressure within the lungs increases.
• Air flows out of the lungs.
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10.4 Mechanism of Breathing
Expiration
Rib cage
moves
down and
in.
Internal intercostal muscles
pull the ribs inward during
forced expiration.
Diaphragm relaxes
and moves up.
air out
When
pressure
in lungs
increases,
air is
pushed out.
b. Expiration
Figure 10.8b The thoracic cavity during expiration.
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10.4 Mechanism of Breathing
Different volumes of air during
breathing
• Tidal volume – the small amount of air that usually
moves in and out with each breath
• Vital capacity – the maximum volume of air that can
be moved in plus the maximum amount that can be
moved out during one breath
• Inspiratory and expiratory reserve volume – the
increased volume of air moving in or out of the body
• Residual volume – the air remaining in the lungs
after exhalation
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10.4 Mechanism of Breathing
Visualizing the vital capacity
5,800
maximum
expiration
Average Lung Volume (ml)
4,800
maximum
inspiration
inspiratory
reserve
volume
vital
capacity
3,600
2,900
2,400
tidal
volume
total
Lung
capacity
expiratory
reserve
volume
1,200
residual
volume
0
residual
volume
© Veronique Burger/Science Source
Figure 10.9 Measuring the vital capacity of the lungs.
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10.5 Control of Ventilation
How is breathing controlled by
the nervous system?
• Nervous control
– Respiratory control center in the brain
(medulla oblongata) sends out nerve
impulses to contract muscle for inspiration.
– Sudden infant death syndrome (SIDS) is
thought to occur when this center stops
sending out nerve signals.
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10.5 Control of Ventilation
How is breathing controlled by
the nervous system?
brain
Respiratory center:
region of the brain that
automatically regulates
breathing
Intercostal nerves
stimulate the intercostal
muscles to contract.
External intercostal muscles
help expand the thoracic
cavity by contracting.
Phrenic nerve
stimulates the diaphragm
to contract.
Diaphragm
helps expand the thoracic
cavity by flattening when
it contracts.
Figure 10.10 The control of
breathing by the respiratory center.
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10.5 Control of Ventilation
How is breathing chemically
controlled?
• Chemical control
– Two sets of chemoreceptors sense the
drop in pH: one set is in the brain and the
other in the circulatory system.
– Both are sensitive to carbon dioxide levels
that change blood pH due to metabolism.
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10.6 Gas Exchanges in the Body
Exchange of gases in the body
• Oxygen and carbon dioxide are exchanged.
• The exchange of gases is dependent on
diffusion.
• Partial pressure is the amount of pressure each
gas exerts (PCO2 or PO2).
• Oxygen and carbon dioxide will diffuse from the
area of higher to the area of lower partial
pressure.
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10.6 Gas Exchanges in the Body
External respiration
• Exchange of gases between the lung alveoli
and the blood capillaries.
• PCO2 is higher in the lung capillaries than the
air, thus CO2 diffuses out of the plasma into
the lungs.
• The partial pressure pattern for O2 is just the
opposite, so O2 diffuses the red blood cells in
the lungs.
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10.6 Gas Exchanges in the Body
External respiration
Carbon dioxide transport:
H+ + HCO3H2CO3
Oxygen transport:
Hb + O2
carbonic
anhydrase
H2O + CO2
HbO2
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10.6 Gas Exchanges in the Body
The movement of oxygen and
carbon dioxide in the body
alveolus
plasma
H+ + HCO–3
External respiration
Hb H+
CO2
pulmonary
capillary
HCO–3
RBC
H2CO3
CO2
Hb O2
H2O
RBC
O2
Hb CO2
pulmonary
capillary
O2
alveolus
CO2 exits blood
CO2
a.
plasma
O2 enters blood
O2
lung
pulmonary artery
pulmonary vein
heart
tissue cells
systemic vein
systemic artery
HCO–3
H+ + HCO–3
plasma
plasma
systemic
capillary
RBC
Figure 10.11
Movement of gases
during external and
internal respiration.
CO2
O2
RBC
systemic
capillary
Hb H+ H2CO3
CO2
H2O
Hb
Internal respiration
Hb CO2
tissue
fluid
CO2 enters blood
b.
tissue
cell
tissue
cell
tissue
fluid
O2 exits blood
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10.6 Gas Exchanges in the Body
Internal respiration
• The exchange of gases between the blood in
the capillaries outside of the lungs and the
tissue fluid.
• PO2 is higher in the capillaries than the tissue
fluid, thus O2 diffuses out of the blood into
the tissues.
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10.6 Gas Exchanges in the Body
Internal respiration
Oxyhemoglobin gives up oxygen:
HbO2
Hb + O2
Most CO2 is carried as a bicarbonate ion:
CO2 + H2O
carbonic
anhydrase
H2CO3
H+ + HCO3-
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10.7 Respiration and Health
Upper respiratory tract
infections
• Sinusitis – blockage of sinuses
• Otitis media – infection of the middle ear
• Tonsillitis – inflammation of the tonsils
• Laryngitis – infection of the larynx that leads
to loss of voice
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10.7 Respiration and Health
Lower respiratory tract disorders
• Pneumonia – infection of the lungs with thick,
fluid build up
• Tuberculosis – bacterial infection that leads to
tubercles (collections of encapsulated bacteria)
• Pulmonary fibrosis – lungs lose elasticity
because fibrous connective tissue builds up in
the lungs, usually because of inhaled particles
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10.7 Respiration and Health
Lower respiratory tract disorders
• Emphysema – chronic, incurable disorder in
which alveoli are damaged, and thus the surface
area for gas exchange is reduced
• Asthma – bronchial tree becomes irritated
causing breathlessness, wheezing, and
coughing
• Lung cancer – uncontrolled cell division in the
lungs that is often caused by smoking and can
lead to death
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10.7 Respiration and Health
Some Diseases and Disorders
of the Respiratory System
mucus
Pneumonia
Alveoli fill with pus and fluid,
making gas exchange difficult.
Bronchitis
Airways are inflamed due
to infection (a cute) or due to
an irritant (chronic). Coughing
brings up mucus and pus.
asbestos
body
tubercle
Pulmonary Fibrosis
Fibrous connective tissue
builds up in lungs, reducing
their elasticity.
Pulmonary Tuberculosis
Tubercles encapsulate
bacteria, and elasticity of
lungs is reduced.
Emphysema
Alveoli burst and fuse into
enlarged air spaces. Surface area
for gas exchange is reduced.
Figure 10.12 Some diseases and disorders of the respiratory system.
Asthma
Airways are inflamed due
to irritation, and bronchioles
constrict due to muscle spasms.
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10.7 Respiration and Health
Things you should know about
tobacco and health
• All forms of tobacco can cause damage.
• Smoking increases a person’s chance of lung,
mouth, larynx, esophagus, bladder, kidney,
pancreatic, stomach, and cervix cancers.
• Smoking also increases the chance of chronic
bronchitis, emphysema, heart disease, stillbirths,
and harm to an unborn child.
• Passive smoke can increase a nonsmoker’s
chance of pneumonia, bronchitis, and lung cancer.
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