Transcript Lungs

Respiration
• Major function is to supply the body with
oxygen and dispose of carbon dioxide
• Involves both the respiratory and the
circulatory systems
• Four processes that supply the body with
O2 and dispose of CO2
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Respiration
• Pulmonary ventilation
(breathing):
movement of air into and out
of the lungs
Respiratory
system
• External respiration: O2 and CO2
exchange between the lungs
and the blood
• Transport of Gases: O2 and CO2
in the blood
• Internal respiration: O2 and CO2
exchange between systemic
blood vessels and tissues
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Circulatory
system
Respiratory System: Functional Anatomy
Major organs include:
• Nose, nasal cavity, and paranasal sinuses
• Pharynx
• Larynx
• Trachea
• Bronchi and their branches
• Lungs and alveoli
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Nasal cavity
Nostril
Oral cavity
Pharynx
Larynx
Trachea
Carina of
trachea
Right main
(primary)
bronchus
Right lung
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Left main
(primary)
bronchus
Left lung
Diaphragm
Figure 22.1
Functional Anatomy–
consists of 2 zones
Respiratory zone: site of gas exchange
• Microscopic structures: respiratory bronchioles,
alveolar ducts, and alveoli
Conducting zone: passageways leading to gas
exchange sites
• Includes all other respiratory structures
Respiratory muscles: diaphragm and other muscles
that promote ventilation
Note: functions in respiratory system but truly part of
skeletal system
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The Nose
Functions
• Provides an airway for respiration
• Moistens and warms the entering air
• Filters and cleans inspired air
• Serves as a resonating chamber for speech
• Houses olfactory receptors
• Useful for storing beads, corn, and other
small objects…see visual aid
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The Nose
Two regions: external nose and nasal cavity
1.External nose: root, bridge, dorsum nasi,
and apex
• Philtrum: a shallow vertical groove
inferior to the apex
• Nostrils (nares): bounded laterally by
the alae
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Epicranius,
frontal belly
Root and
bridge of
nose
Dorsum nasi
Ala of nose
Apex of nose
Naris (nostril)
Philtrum
(a) Surface anatomy
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Figure 22.2a
Frontal bone
Nasal bone
Septal cartilage
Maxillary bone
(frontal process)
Lateral process of
septal cartilage
Minor alar cartilages
Dense fibrous
connective tissue
Major alar
cartilages
(b) External skeletal framework
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Figure 22.2b
The Nose
2. Nasal cavity: in and posterior to the
external nose
• Divided by a midline nasal septum
• Posterior nasal apertures (choanae) open
into the nasal pharynx
• Roof: ethmoid and sphenoid bones
• Floor: hard and soft palates
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Nasal Cavity
Vestibule: nasal cavity superior to the nostrils lined
with sebaceous and sweat glands and many hair
follicles
• Vibrissae hairs that filter
coarse particles (dust, pollen)
from inspired air
The rest of the nasal cavity is lined with 2 types of
mucous membranes
Note: there is a
1. Olfactory mucosa
difference between
• Lines the superior nasal cavity
mucous and
mucus!!!
• Contains smell receptors
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Nasal Cavity
2. Respiratory mucosa
• Pseudostratified ciliated columnar
epithelium
• Mucous and serous secretions contain
lysozyme and defensins
• Cilia move contaminated mucus posteriorly
to throat
• Inspired air is warmed by networks of
capillaries and veins
• Sensory nerve endings triggers sneezing
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Cribriform plate
of ethmoid bone
Sphenoid sinus
Posterior nasal
aperture
Nasopharynx
Pharyngeal tonsil
Opening of
pharyngotympanic
tube
Uvula
Frontal sinus
Nasal cavity
Nasal conchae
(superior, middle
and inferior)
Nasal meatuses
(superior, middle,
and inferior)
Nasal vestibule
Nostril
Oropharynx
Palatine tonsil
Isthmus of the
fauces
Hard palate
Soft palate
Tongue
Lingual tonsil
Laryngopharynx
Esophagus
Trachea
(c) Illustration
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Larynx
Epiglottis
Vestibular fold
Thyroid cartilage
Vocal fold
Cricoid cartilage
Thyroid gland
Hyoid bone
Figure 22.3c
Nasal Cavity
Superior, middle, and inferior nasal conchae
• Protrude from the lateral walls
• Increase mucosal area
• Enhance air turbulence
This air turbulence helps clean, moisten
and warm incoming air before it reaches
the throat.
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Functions of the Nasal Mucosa and
Conchae
• During inhalation, the conchae and nasal
mucosa
• Filter, heat, and moisten air
• During exhalation these structures
• Reclaim heat and moisture
Bat in the Cave Cam
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Paranasal Sinuses
• In frontal, sphenoid, ethmoid, and maxillary
bones
What functions do the sinuses perform?
• Lighten the skull and help to warm and
moisten the air
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Pharynx = Throat
• Muscular tube that connects to the
• Nasal cavity and mouth superiorly
• Larynx and esophagus inferiorly
• Divided into 3 regions
• Nasopharynx
• Oropharynx
• Laryngopharynx
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Pharynx
Nasopharynx
Oropharynx
Laryngopharynx
(b) Regions of the pharynx
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Figure 22.3b
Nasopharynx
• Air passageway only located posterior to the
nasal cavity
• Soft palate and uvula close nasopharynx
during swallowing
• Pharyngeal tonsil (adenoids) on posterior wall
• Pharyngotympanic (auditory) tubes open into
the lateral walls
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Oropharynx
• Passageway for food and air from the level
of the soft palate to the epiglottis
• Lining of stratified squamous epithelium
• Isthmus of the fauces: opening to the oral
cavity
• Palatine tonsils in the lateral walls of
fauces
• Lingual tonsil on the posterior surface of
the tongue
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Laryngopharynx
• Passageway for food and air
• Posterior to the upright epiglottis
• Extends to the larynx, where it is also
continuous with the esophagus
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Cribriform plate
of ethmoid bone
Sphenoid sinus
Posterior nasal
aperture
Nasopharynx
Pharyngeal tonsil
Opening of
pharyngotympanic
tube
Uvula
Frontal sinus
Nasal cavity
Nasal conchae
(superior, middle
and inferior)
Nasal meatuses
(superior, middle,
and inferior)
Nasal vestibule
Nostril
Oropharynx
Palatine tonsil
Isthmus of the
fauces
Hard palate
Soft palate
Tongue
Lingual tonsil
Laryngopharynx
Esophagus
Trachea
(c) Illustration
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Larynx
Epiglottis
Vestibular fold
Thyroid cartilage
Vocal fold
Cricoid cartilage
Thyroid gland
Hyoid bone
Figure 22.3c
And Breath…..
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Larynx
• Attaches to the hyoid bone and opens into
the laryngopharynx
• Continuous with the trachea
• Functions
1. Provides a patent airway
2. Routes air and food into proper channels
3. Voice production
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Larynx
Cartilages of the larynx
• Hyaline cartilage except for the epiglottis
• Thyroid cartilage with laryngeal prominence
(Adam’s apple)
• Ring-shaped cricoid cartilage
• Paired arytenoid, cuneiform, and corniculate
cartilages
Epiglottis: elastic cartilage; covers the laryngeal
inlet during swallowing
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Epiglottis
Thyrohyoid
membrane
Body of hyoid bone
Thyroid cartilage
Laryngeal prominence
(Adam’s apple)
Cricothyroid ligament
Cricoid cartilage
Cricotracheal ligament
Tracheal cartilages
(a) Anterior superficial view
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Figure 22.4a
Epiglottis
Body of hyoid bone
Thyrohyoid
membrane
Cuneiform cartilage
Corniculate cartilage
Arytenoid cartilage
Arytenoid muscles
Cricoid cartilage
Thyrohyoid membrane
Fatty pad
Vestibular fold
(false vocal cord)
Thyroid cartilage
Vocal fold
(true vocal cord)
Cricothyroid ligament
Cricotracheal ligament
Tracheal cartilages
(b) Sagittal view; anterior surface to the right
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Figure 22.4b
Larynx
• Vocal ligaments
• Attach the arytenoid cartilages to the
thyroid cartilage
• Contain elastic fibers
• Form core of vocal folds (true vocal cords)
• Opening between them is the glottis
• Folds vibrate to produce sound as air
rushes up from the lungs
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Larynx
• Vestibular folds (false vocal cords)
• Superior to the vocal folds
• No part in sound production
• Help to close the glottis during swallowing
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Base of tongue
Epiglottis
Vestibular fold
(false vocal cord)
Vocal fold
(true vocal cord)
Glottis
Inner lining of trachea
Cuneiform cartilage
Corniculate cartilage
(a) Vocal folds in closed position;
closed glottis
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(b) Vocal folds in open position;
open glottis
Figure 22.5
Voice Production
• Speech: intermittent release of expired air while
opening and closing the glottis
• Pitch is determined by the length and tension of
the vocal cords
• Loudness depends upon the force of air
• Chambers of pharynx, oral, nasal, and sinus
cavities amplify and enhance sound quality
• Sound is “shaped” into language by muscles of the
pharynx, tongue, soft palate, and lips
The Larynx at Work
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Larynx
• Vocal folds may act as a sphincter to
prevent air passage
• Example: Valsalva’s maneuver
• Glottis closes to prevent exhalation
• Abdominal muscles contract
• Intra-abdominal pressure rises
• Helps to empty the rectum or stabilizes the
trunk during heavy lifting
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Trachea
• Windpipe: extends from the larynx into the
mediastinum
• Wall composed of three layers
1. Mucosa: ciliated pseudostratified epithelium
with goblet cells
2. Submucosa: connective tissue with seromucous
glands
3. Adventitia: outermost layer made of
connective tissue that encases the C-shaped
rings of hyaline cartilage
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Trachea
• Trachealis muscle
• Connects posterior parts of cartilage rings
• Contracts during coughing to expel mucus
• Carina
• Last tracheal cartilage
• Point where trachea branches into two
bronchi
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Posterior
Mucosa
Submucosa
Esophagus
Trachealis
muscle
Lumen of
trachea
Seromucous gland
in submucosa
Hyaline cartilage
Adventitia
Anterior
(a) Cross section of the trachea and esophagus
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Figure 22.6a
Bronchi and Subdivisions
• Branch off the
trachea into the rt.
and lt. primary bronchi
• Air passages branch
repeatedly
• Branching pattern
called the bronchial
tree
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Conducting Zone Structures
• Nose  Pharynx  Larynx  Trachea 
right and left main (primary) bronchi
• Right main bronchus is wider, shorter, and
more vertical than the left = choking hazard
• Each main bronchus branches into lobar
(secondary) bronchi (three right, two left)
• Each lobar bronchus supplies one lobe
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Conducting Zone Structures
• Each lobar bronchus branches into
segmental (tertiary) bronchi
• Segmental bronchi divide repeatedly
• Bronchioles are less than 1 mm in diameter
• Terminal bronchioles are the smallest, less
than 0.5 mm diameter
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Trachea
Middle lobe
of right lung
Superior lobe
of left lung
Left main
(primary)
bronchus
Lobar
(secondary)
bronchus
Segmental
(tertiary)
bronchus
Inferior lobe
of right lung
Inferior lobe
of left lung
Superior lobe
of right lung
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Figure 22.7
Conducting Zone Structures
• From bronchi through bronchioles,
structural changes occur
• Cartilage rings give way to plates; cartilage
is absent from bronchioles
• cilia and goblet (mucus producing) cells
become sparse
• Amount of smooth muscle increases
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Respiratory Zone
• This zone includes the bronchioles, alveolar
ducts, alveolar sacs (clusters of alveoli)
• ~300 million alveoli account for most of the
lungs’ volume and are the main site for gas
exchange
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Alveoli
Alveolar duct
Respiratory
bronchioles
Terminal
bronchiole
Alveolar duct
Alveolar
sac
(a)
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Figure 22.8a
Respiratory Membrane of Alveoli
• Extremely thin air-blood barrier that has
are on one side and blood on the other
• Alveolar walls
• Single layer of type I and type II cells
surrounded by a flimsy basement membrane
and covered in a cobweb of capillaries
• Scattered type II cells secrete surfactant
and antimicrobial proteins
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Terminal bronchiole
Respiratory bronchiole
Smooth
muscle
Elastic
fibers
Alveolus
Capillaries
(a) Diagrammatic view of capillary-alveoli relationships
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Figure 22.9a
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Figure 22.9b
Alveoli
• Surrounded by fine elastic fibers
• Contain open pores that
• Connect adjacent alveoli
• Allow air pressure throughout the lung to be
equalized
• House alveolar macrophages that keep
alveolar surfaces sterile
Fun Fact: we swallow over 2 million
old and dead macrophages per
hour!!!!
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Red blood
cell
Nucleus of type I
(squamous
epithelial) cell
Alveolar pores
Capillary
O2
Capillary
CO2
Alveolus
Alveolus
Type I cell
of alveolar wall
Macrophage
Endothelial cell nucleus
Alveolar
epithelium
Fused basement
membranes of the
Respiratory alveolar epithelium
membrane and the capillary
Red blood cell
endothelium
Alveoli (gas-filled in capillary
Type II (surfactantCapillary
air spaces)
secreting) cell
endothelium
(c) Detailed anatomy of the respiratory membrane
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Figure 22.9c
Lungs
• Occupy all of the thoracic cavity except the
mediastinum
• Costal surface: anterior, lateral, and
posterior surfaces
• Apex: superior tip
• Base: inferior surface that rests on the
diaphragm
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Lungs
Right lung has 3 lobes separated by oblique
and horizontal fissures
Left lung is smaller, separated into 2 lobes
by an oblique fissure
• Cardiac notch of left lung: concavity that
accommodates the heart
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Trachea
Thymus
Lung
Intercostal
muscle
Rib
Parietal pleura
Pleural cavity
Visceral pleura
Apex of lung
Right superior lobe
Horizontal fissure
Heart
(in mediastinum)
Right middle lobe
Oblique fissure
Right inferior lobe
Diaphragm
Base of lung
Left
superior lobe
Oblique
fissure
Left inferior
lobe
Cardiac notch
(a) Anterior view. The lungs flank mediastinal structures laterally.
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Figure 22.10a
Right lung
Right
superior
lobe (3
segments)
Left lung
Left superior
lobe
(4 segments)
Right
middle
lobe (2
segments)
Right
inferior lobe (5 segments)
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Left inferior
lobe (5 segments)
Figure 22.11
Blood Supply
Pulmonary circulation (low pressure, high
volume)
• Pulmonary arteries deliver systemic venous
blood
• Branch profusely, along with bronchi
• Feed into the pulmonary capillary
networks
• Pulmonary veins carry oxygenated blood
from respiratory zones to the heart
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Blood Supply
Systemic circulation (high pressure, low volume)
• Bronchial arteries provide oxygenated blood to
lung tissue
• Arise from aorta and enter the lungs
• Supply all lung tissue except the alveoli
• Bronchial veins anastomose with pulmonary
veins
• Pulmonary veins carry most venous blood back
to the heart
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Pleurae
• Thin, double-layered membrane
• Parietal pleura on thoracic wall and superior
face of diaphragm
• Visceral pleura on external lung surface
• Pleural fluid fills the slit-like pleural cavity
• Provides lubrication and surface tension
See Visual Aid
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Vertebra
Right lung
Parietal
pleura
Visceral
pleura
Pleural
cavity
Pericardial
membranes
Sternum
Posterior
Esophagus
(in mediastinum)
Root of lung
at hilum
• Left main bronchus
• Left pulmonary artery
• Left pulmonary vein
Left lung
Thoracic wall
Pulmonary trunk
Heart (in mediastinum)
Anterior mediastinum
Anterior
(c) Transverse section through the thorax, viewed from above. Lungs,
pleural membranes, and major organs in the mediastinum are shown.
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Figure 22.10c
Mechanics of Breathing
Under Pressure
• Pulmonary ventilation consists of two
phases
1.Inspiration: air flow into the lungs
2.Expiration: air exits the lungs
Average respiratory rate in an adult is 12-18
breaths per minute
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Pressure Relationships in the Thoracic
Cavity
Atmospheric pressure (Patm)
• Pressure exerted by the air surrounding the
body
• 760 mm Hg at sea level
Respiratory pressures are described relative to
Patm
• Negative respiratory pressure is less than Patm
• Positive respiratory pressure is greater than
Patm
• Zero respiratory pressure = Patm
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Intrapulmonary Pressure
Intrapulmonary pressure (Ppul)
• Pressure in the alveoli
• Fluctuates with breathing
• Always eventually equalizes with Patm
(0 respiratory pressure)
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Intrapleural Pressure
Intrapleural pressure (Pip):
• Pressure in the pleural cavity
• Fluctuates with breathing
• Always a negative pressure
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Intrapleural Pressure
Negative Pip is caused by opposing forces
• Two inward forces promote lung collapse
• Elastic recoil of lungs decreases lung size
• Surface tension of alveolar fluid reduces
alveolar size
• One outward force tends to enlarge the
lungs
• Elasticity of the chest wall pulls the
thorax outward
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Pressure Relationships
• If Pip = Ppul the lungs collapse
• The difference in these pressures =
transpulmonary pressure
• Keeps the airways open
• The greater the transpulmonary pressure,
the larger the lungs
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Atmospheric pressure
Parietal pleura
Thoracic wall
Visceral pleura
Pleural cavity
Transpulmonary
pressure
760 mm Hg
–756 mm Hg
= 4 mm Hg
756
760
Lung
Diaphragm
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Intrapleural
pressure
756 mm Hg
(–4 mm Hg)
Intrapulmonary
pressure 760 mm Hg
(0 mm Hg)
Figure 22.12
Homeostatic Imbalance
• Atelectasis (lung collapse) is due to
• Plugged bronchioles  collapse of alveoli
• Wound that admits air into pleural cavity
(pneumothorax)
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Pulmonary Ventilation
• Inspiration and expiration
• Mechanical processes that depend on
volume changes in the thoracic cavity
• Volume changes  pressure changes
• Pressure changes  gases flow to equalize
pressure
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Boyle’s Law
• The relationship between the pressure and
volume of a gas
• Pressure varies inversely with volume
As we decrease volume, we increase pressure
As we increase volume, we decrease pressure
Who likes marshmallows?
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Inspiration
• An active process
• Inspiratory muscles contract
• Thoracic volume increases
• Lungs are stretched and intrapulmonary
volume increases
• Intrapulmonary pressure drops (to 1 mm
Hg)
• Air flows into the lungs, down its pressure
gradient, until Ppul = Patm
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Expiration
• Quiet expiration is normally a passive process
• Inspiratory muscles relax
• Thoracic cavity volume decreases
• Elastic lungs recoil and intrapulmonary volume
decreases
• Intrapulmonary pressure increases (to +1 mm Hg)
• Air flows out of the lungs down its pressure
gradient until pulmonary pressure (Ppul) = 0
• Note: forced expiration is an active process: it
uses abdominal and internal intercostal muscles
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Physical Factors Influencing Pulmonary
Ventilation
• 3 factors hinder air passage and pulmonary
ventilation
1. Airway resistance
2. Alveolar surface tension
3. Lung compliance
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Airway Resistance
• As airway resistance rises, breathing
movements become more strenuous
• Severely constricted or obstructed
bronchioles
• Can prevent life-sustaining ventilation
• Can occur during acute asthma attacks and
stop ventilation
• Epinephrine dilates bronchioles and reduces
air resistance
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Alveolar Surface Tension
Surface tension
• Attracts liquid molecules to one another at
a gas-liquid interface
• Resists any force that tends to increase the
surface area of the liquid
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Alveolar Surface Tension
• Surfactant
• Detergent-like lipid and protein complex
produced by type II alveolar cells
• Reduces surface tension of alveolar fluid
and discourages alveolar collapse
• Insufficient quantity in premature infants
causes infant respiratory distress syndrome
Want to see a magic trick?
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Lung Compliance
• A measure of the change in lung volume
that occurs with a given change in
transpulmonary pressure
• Normally high due to
• Elasticity of the lung tissue
• Alveolar surface tension
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Lung Compliance
• Diminished by
• Nonelastic scar tissue (fibrosis)
• Reduced production of surfactant
• Decreased flexibility of the thoracic cage
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Lung Compliance
• Homeostatic imbalances that reduce
compliance
• Deformities of thorax
• Ossification of the costal cartilage
• Paralysis of intercostal muscles
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