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Chapter 19
Respiratory System
Respiration is the process of exchanging gases between the
atmosphere and body cells. Consists of the following
events:
• ventilation
• external respiration
• transport
• internal respiration
• cellular respiration
1
Two Main Divisions
• Upper Respiratory
– Consists of the
nose and throat
(pharynx)
• Lower Respiratory
– Consists of the
larynx, trachea,
bronchi and lungs
2
Organs of the
Respiratory System
3
Organs of the
Respiratory System
4
Upper Respiratory Tract
5
Mucous in Respiratory Tract
Cilia move mucus and trapped particles from the nasal cavity
to the pharynx
6
Nose
• External portion
– Composed of
cartilage covered by
skin
• Internal portion
– Nasal Cavity
– Large cavity in the
skull inferior to the
cranium and superior
to the mouth
7
Nose
• Nasal Septum
– Vertical partition that
divides the nasal
cavity
– Anterior portion
made of cartilage
– Posterior portion
made of the vomer
bone and the
perpendicular plate
of the ethmoid bone
8
Clinical Application: Nose
• Rhinoplasty
– nose job”
– Surgical procedure in
which the external
structures are altered
– Usually for cosmetic
reasons
– Occasionally to repair
fractures or deviated
septum
• Septoplasty– Surgery to correct a
deviated (crooked)
septum
– Often done to correct
breathing problems
resulting from
blockages
– Can also be cosmetic
9
Sinuses
Air-filled spaces in maxillary, frontal, ethmoid, and
sphenoid bones
10
Nose Physiology
• Interior specialized for 3 functions
1. Air is warmed, moistened and filtered
2. Olfactory stimuli received--only direct
stimulus to the brain
3. Large, resonating chamber helps produce
speech sounds
11
Pharynx
12
Pharynx
• Funnel-shaped
structure about 13
cm long--starts at the
back of the nasal
cavity and extends to
the cricoid cartilage
of the larynx
• 2 functions
– Passage for food and
air
– Resonating chamber
for speech sounds 13
Pharynx
•
3 parts of the pharynx
•
–
–
Nasopharynx
Posterior to the internal nasal cavity and
extends to the plane of the soft palate
Exchanges small amounts of air with the
auditory (Eustachian) tubes
•
Equalizes air pressure between atmospheric air
and air pressure in the middle ear
14
Pharynx
• Oropharynx
– Posterior to the oral cavity
– Extends from the soft palate to the level of
the hyoid bone
– Contains the opening from the mouth
– Common passageway for air, food and drink
15
Pharynx
• Laryngopharynx
– Extends from the
hyoid bone level
and becomes
continuous with
the esophagus
16
Larynx
• Short passageway that connects the
pharynx with the trachea
• Along the midline of the neck between
the C4 (cervical #4) and C6 (cervical #6)
vertebrae
• Contains: thyroid cartilage, epiglottis,
cricoid cartilage, and glottis
17
Larynx
18
Larynx
• Thyroid Cartilage
– 2 plates of cartilage that form the anterior
wall of the larynx
– Typically larger in males
• “Adam’s apple”
19
Larynx
• Epiglottis
– Large leaf-shaped piece of cartilage lying on top of
the larynx
– “Stem” attached to the thyroid cartilage
– “Leaf” moves up and down like a trap door
– Swallowing causes the larynx to move up, which
causes the epiglottis to cover the glottis
20
Larynx
• Glottis
– Vocal folds and the space between the folds
– Voice Production:
• Muscles contract, pull on the elastic ligaments,
which stretch the vocal folds out into the air
passage (narrows the glottis)
• Air is pushed through and vibrates
–
–
–
–
Sends sound waves into the pharynx, nose and mouth
Higher pressure=louder sounds
Pitch controlled by vocal fold tension (tight=high)
Male folds are thicker, producing lower sounds
21
Vocal Cords
22
Larynx
• Cricoid Cartilage
– Forms anterior wall of the larynx
– Attached to the first ring of cartilage of the
trachea
23
Trachea
Passageway for air
12 cm long, 2.5 cm
diameter
Anterior to the esophagus
Extends from the larynx to
the 5th thoracic vertebra
16-20 incomplete rings of
hyaline cartilage
Allows for anterior
protection and posterior
flexibility for swallowing
24
Tracheostomy
•Performed to allow air to
bypass an obstruction
within the larynx
•Skin incision, followed by
a small longitudinal
incision into the trachea
Patient inspires through a
tube placed in the incision
25
Intubation
• Tube placed into the
mouth or nose and
forced through the
larynx and trachea
• Tube wall pushes back
any obstruction
• Mucus blockage
sucked out through the
tube
QuickTime™ and a
decompressor
are needed to see this picture.
26
Bronchial Tree
27
Bronchi
• Trachea divides at the
sternum
• Right and left primary
bronchus
• Right primary bronchus
is more vertical, shorter
and wider than the left
• Made of incomplete
rings of cartilage and
lined by pseudostratified
ciliated epithelium
QuickTime™ and a
decompressor
are needed to see this picture.
28
Secondary Bronchi
• “Lobar”
• Primary split after
entering each lung
• Secondary bronchi go to
each lobe of each lung
• Secondary split into
tertiary (segmental)
bronchi
• divide into bronchioles
• split into terminal
bronchioles
QuickTime™ and a
decompressor
are needed to see this picture.
29
Bronchi
• More Branching = Tissue Changes
• 1st- rings of cartilage replace by plates that disappear in
the bronchioles
• 2nd- as cartilage amount decreases, smooth muscle
increases
• 3rd-epithelium changes from pseudostratified ciliated to
simple cuboidal in the terminal bronchioles
30
Clinical Application: Bronchi
• Asthma
• Smooth muscle of
bronchioles contract,
reducing the diameter of
the airway
QuickTime™ and a
decompressor
are needed to see this picture.
• Inhalers (bronchioles
dilators) relax the
muscle and open the
airways
31
Alveoli
• Important in gas exchange
• Surrounded by capillaries
• 3 specialized cells in alveolar sac
– Squamous pulmonary epithelial cells
• allow for diffusion of O2 & CO2 from
surrounding vascular cells
– Septal cells--cuboidal cells
• Produce surfactant--phospholipid substance that
lowers surface tension
– Alveolar macrophages (dust cells)-phagocytic cells
32
Alveoli
33
Clinical Application: Alveoli
• Nebulization
– Administering
medication in the
form of droplets that
are suspended in air
– Patient inhales the
medication as a fine
mist
QuickTime™ and a
decompressor
are needed to see this picture.
34
Diffusion Across Respiratory
Membrane
35
Lungs
36
Lungs
• 2 layers of membrane (pleural
membrane) enclose and protect each lung
– Visceral Pleura - covers lungs
– Parietal Pleura - attached to the wall of the
thoracic cavity
– Pleural cavity - space between each pleura,
filled with fluid
37
Transverse Section of Lungs
38
Lungs
• Base
– broad inferior
portion that is
concave and fits over
the diaphragm
• Apex
– narrow superior
portion
• Costal surface
– touch the ribs
39
Lungs
• Hilus
– area in which bronchi,
blood vessels, lymphatic
vessels and nervous
tissue enter and leave the
lungs
• Cardiac notch
– ONLY on the left lung
Right lung is thicker,
broader and shorter
than left
40
Lungs
• Lobes and Fissures
– Superior lobe
• above oblique fissure
• Both lungs
– Inferior lobe
• below oblique fissure
• Both lungs
QuickTime™ and a
TIFF (Uncompressed) decompressor
are needed to see this picture.
– Middle lobe
• ONLY in the right
lung
• Subdivision of right
superior lobe
41
Lungs
• Oblique fissure
– extends downward
and forward
– Both lungs
• Horizontal fissure
– only in the right
lung
– Divides superior
and middle lobes
QuickTime™ and a
TIFF (Uncompressed) decompressor
are needed to see this picture.
42
Lungs
**Each lobe receives
its own secondary
(lobar) bronchus
**Each secondary
bronchus named
after the lobe it
serves
43
Lungs
• Bronchopulmonary Segment
– Section of lung that surrounds a tertiary
bronchus
44
Lungs
• Lobules
– Small compartments of a
bronchopulmonary segment
– Wrapped in elastic connective tissue
– Contain lymphatic vessels, arteriole, venule,
and branch from terminal bronchiole
• Terminal bronchioles split into respiratory
bronchioles, which splits into alveolar ducts
• Alveolar ducts lead to alveolar sacs
45
Breathing Mechanism
• Breathing or ventilation is the movement of air
from outside the body into the bronchial tree and
alveoli
• air movements of inspiration and expiration
• changes in the size of the thoracic cavity due
to changes in pressure
46
Inspiration
• Moving the
plunger of a syringe
causes air to move in
or out
• Air movements in
and out of the lungs
occur in much the
same way
47
Inspiration
• Boyle’s Law
– Pressure of a
gas in a closed
container is
inversely
proportional to
the volume of
the container
48
Lungs at Rest
When lungs are at rest, the pressure on the inside of the
lungs is equal to the pressure on the outside of the thorax
49
Inspiration
• Intra-alveolar
pressure decreases to
about 758mm Hg as
the thoracic cavity
enlarges
• Atmospheric
pressure forces air
into the airways
50
Inspiration
Shape of thorax at end
of normal inspiration
Shape of thorax at end of maximal
inspiration aided by contraction of
sternocleidomastoid and pectoralis minor
muscles
51
Inspiration
• Lung volume
increases 2 ways:
– Diaphragm
• Main inspiratory
muscle
• Contraction causes it
to flatten and increase
vertical dimension of
thoracic cavity
• May increase 1 cm to
10 cm
• Accounts for
movement of 75% of
air entering lungs
52
Inspiration
– External Intercostal
Muscles
• contractions pull ribs
up pushing sternum
out
• Increases diameter of
thoracic cavity
53
Major Events in Inspiration
54
Expiration
• due to elastic recoil of the lung tissues and abdominal organs
55
Expiration
• NORMAL
expiration is a
passive process
• Active process
during high levels
of ventilation
56
Maximal Expiration
• contraction of
abdominal wall
muscles forcing
diaphragm up
• contraction of
posterior internal
intercostal muscles
57
Major Events in Expiration
58
Ventilation
• 1 ventilation (respiration) = 1 inspiration
+ 1 expiration
• Normal adults ventilate about 12 times
per minute
59
Respiratory Volumes and
Capacities
60
Respiratory Volumes and
Capacities
• Pulmonary Reserve volume
– Inhaling deeply
– 3100 ml above the tidal volume
• Expiratory Reserve volume
– Forcibly exhaling
– 1200ml below the tidal volume
61
Respiratory Volumes and
Capacities
• Residual volume
– Amount left after expiratory reserve volume is
expelled
– Because some air remains in airways inside the
lungs
– 1200ml
• Minimal volume
– Lungs with only minimal volume will not float
– Fetal lungs contain no air, so lungs of stillborn will
not float
62
External Respiration
• Exchange of oxygen and carbon dioxide
between the alveoli of lungs and the pulmonary
blood capillaries
• Alveolar air has a partial pressure of oxygen of
105-mmHg pO2
• Dalton’s Law
– Each gas in mixture exerts its own pressure
as if all the other gases were not present
63
External Respiration &
Dalton’s Law
• pO2 of deoxygenated blood in the alveolar
capillaries is only 40 mmHg
• O2 diffuses from alveoli into the deoxygenated
blood until equilibrium is reached
• gives oxygenated blood a pO2 of 105 mmHg
(equal to atmospheric air)
• CO2 diffuses in the opposite direction
• pCO2 in deoxygenated blood is 45 mmHg-
alveolar air is 40 mmHg
64
Alveolar Ventilation
Minute ventilation
• Tidal volume
multiplied by
breathing rate
• Amount of air
that is moved into
the respiratory
passageways
Alveolar ventilation rate
• Major factor affecting
concentrations of oxygen
and carbon dioxide in the
alveoli
• Volume of air that
reaches alveoli
• Tidal volume minus
physiologic dead space
then multiplied by
breathing rate
65
Respiratory Center
66
Respiratory Center
67
Factors Affecting Breathing
Decreased blood
oxygen concentration
stimulates peripheral
chemoreceptors in the
carotid and aortic
bodies
68
Factors Affecting Breathing
• motor impulses travel from
the respiratory center to the
diaphragm and external
intercostal muscles
• contraction of these muscles
causes lungs to expand
• expansion stimulates stretch
receptors in the lungs
• inhibitory impulses from
receptors to respiratory
center prevent overinflation
of lungs
69
Factors Affecting Breathing
70
Adaptations That Increase
Effectiveness
• Thickness
– Alveolar sac- capillary complex only 2 cells layers
thick
• Surface area
– More surface area the more diffusion possible
– Surface area of alveoli in the lungs is about 70m2
71
Adaptations That Increase
Effectiveness
• Large number of capillaries
– Allow 100 ml of blood to participate in gas
exchange at one time
• Narrow Capillaries
– Allow RBCs to flow through in single file
– Provides maximum exposure
72
Alveoli
• gas exchanges between the air and blood
occur within the alveoli
• alveolar pores allow air to pass from one
alveolus to another
73
Respiratory Membrane
• consists of the walls of the alveolus and the capillary
74
Diffusion Through
Respiratory Membrane
Gases are exchanged between alveolar air and capillary
blood because of differences in partial pressure
75
Factors Affecting Efficiency
• Altitude
– atmospheric pO2 decreases as altitude
increases
• Surface area
– damaged surface area (smoke, cancer, etc.)
• Small volumes
– certain drugs slow respiration rate
76
Life-Span Changes
• Reflect accumulation of environmental influences
• Reflect the effects of aging in other organ systems
• Cilia less active
• Mucous thickens
• Swallowing, gagging, and coughing reflexes slow
• Macrophages in lungs lose efficiency
• Increased susceptibility to respiratory infections
• “Barrel chest” may develop
• Bronchial walls thin and collapse
• Dead space increases
77
Clinical Application:
Cigarette Smoking
• Cilia disappear
• Excess mucus produced
• Lung congestion
increases lung infections
• Lining of bronchioles
thicken
• Bronchioles lose elasticity
• Emphysema fifteen times
more common
• Lung cancer more
common
• Much damage repaired
when smoking stops
78