Transcript Respiratory system powerpoint #1

The Respiratory System
• Major function-respiration
– Supply body with O2 for cellular respiration;
dispose of CO2, a waste product of cellular
respiration
– Its four processes involve both respiratory and
circulatory systems
• Also functions in olfaction and speech
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Processes of Respiration
• Pulmonary ventilation (breathing)movement of air into and out
of lungs
• External respiration-O2 and CO2
exchange between lungs and blood
• Transport-O2 and CO2 in blood
• Internal respiration-O2 and CO2
exchange between systemic blood
vessels and tissues
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Respiratory
system
Circulatory
system
Respiratory System: Functional Anatomy
• Major organs
– Nose, nasal cavity, and paranasal sinuses
– Pharynx
– Larynx
– Trachea
– Bronchi and their branches
– Lungs and alveoli
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Figure 22.1 The major respiratory organs in relation to surrounding structures.
Nasal cavity
Oral cavity
Nostril
Pharynx
Larynx
Trachea
Carina of
trachea
Right main
(primary)
bronchus
Right
lung
Left main
(primary)
bronchus
Left lung
Diaphragm
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Functional Anatomy
• Respiratory zone-site of gas exchange
– Microscopic structures-respiratory
bronchioles, alveolar ducts, and alveoli
• Conducting zone-conduits to gas
exchange sites
– Includes all other respiratory structures;
cleanses, warms, humidifies air
• Diaphragm and other respiratory muscles
promote ventilation
PLAY
Animation: Rotating face
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The Nose
• Functions
– Provides an airway for respiration
– Moistens and warms entering air
– Filters and cleans inspired air
– Serves as resonating chamber for speech
– Houses olfactory receptors
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The Nose
• Two regions-external nose and nasal
cavity
• External nose-root, bridge, dorsum nasi,
and apex
– Philtrum-shallow vertical groove inferior to
apex
– Nostrils (nares)-bounded laterally by alae
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Figure 22.2a The external nose.
Epicranius,
frontal belly
Root and
bridge of nose
Dorsum nasi
Ala of nose
Apex of nose
Naris (nostril)
Surface anatomy
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Figure 22.2b The external nose.
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
External skeletal framework
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The Nose
• Nasal cavity-within and posterior to
external nose
– Divided by midline nasal septum
– Posterior nasal apertures (choanae) open
into nasal pharynx
– Roof-ethmoid and sphenoid bones
– Floor–hard (bone) and soft palates (muscle)
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Nasal Cavity
• Nasal vestibule-nasal cavity superior to
nostrils
– Vibrissae (hairs) filter coarse particles from
inspired air
• Rest of nasal cavity lined with mucous
membranes
– Olfactory mucosa
– Respiratory mucosa
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Nasal Cavity
• Olfactory mucosa contains olfactory
epithelium
• Respiratory mucosa
– Pseudostratified ciliated columnar epithelium
– Mucous and serous secretions contain
lysozyme and defensins
– Cilia move contaminated mucus posteriorly to
throat
– Inspired air warmed by plexuses of capillaries
and veins
– Sensory nerve endings trigger sneezing
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Figure 22.3b The upper respiratory tract.
Cribriform plate
of ethmoid bone
Sphenoid sinus
Frontal sinus
Nasal cavity
Nasal conchae
(superior, middle
and inferior)
Nasal meatuses
(superior, middle,
and inferior)
Nasal vestibule
Posterior nasal
aperture
Nasopharynx
Pharyngeal tonsil
Opening of
pharyngotympanic tube
Uvula
Nostril
Oropharynx
Palatine tonsil
Isthmus of the
fauces
Hard palate
Soft palate
Tongue
Lingual tonsil
Laryngopharynx
Esophagus
Larynx
Epiglottis
Vestibular fold
Thyroid cartilage
Vocal fold
Cricoid cartilage
Trachea
Thyroid gland
Illustration
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Hyoid bone
Figure 22.3a The upper respiratory tract.
Olfactory nerves
Olfactory
epithelium
Superior nasal concha
and superior nasal meatus
Mucosa
of pharynx
Middle nasal concha
and middle nasal meatus
Tubal
tonsil
Inferior nasal concha
and inferior nasal meatus
Pharyngotympanic
(auditory) tube
Nasopharynx
Hard palate
Soft palate
Uvula
Photograph
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Nasal Cavity
• Nasal conchae-superior, middle, and
inferior
– Protrude medially from lateral walls
– Increase mucosal area
– Enhance air turbulence
• Nasal meatus
– Groove inferior to each concha
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Functions of the Nasal Mucosa and
Conchae
• During inhalation, conchae and nasal
mucosa
– Filter, heat, and moisten air
• During exhalation these structures
– Reclaim heat and moisture
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Paranasal Sinuses
• In frontal, sphenoid, ethmoid, and
maxillary bones
• Lighten skull; secrete mucus; help to warm
and moisten air
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Homeostatic Imbalance
• Rhinitis
– Inflammation of nasal mucosa
– Nasal mucosa continuous with mucosa of
respiratory tract  spreads from nose 
throat  chest
– Spreads to tear ducts and paranasal sinuses
causing
• Blocked sinus passageways  air absorbed 
vacuum  sinus headache
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Pharynx
• Muscular tube from base of skull to C6
– Connects nasal cavity and mouth to larynx
and esophagus
– Composed of skeletal muscle
• Three regions
– Nasopharynx
– Oropharynx
– Laryngopharynx
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Figure 22.3c The upper respiratory tract.
Pharynx
Nasopharynx
Oropharynx
Laryngopharynx
Regions of the pharynx
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Nasopharynx
• Air passageway posterior to nasal cavity
• Lining - pseudostratified columnar
epithelium
• Soft palate and uvula close nasopharynx
during swallowing
• Pharyngeal tonsil (adenoids) on posterior
wall
• Auditory tubes drain and equalize
pressure in middle ear; open into lateral
walls
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Oropharynx
• Passageway for food and air from level of
soft palate to epiglottis
• Lining of stratified squamous epithelium
• Isthmus of fauces-opening to oral cavity
• Palatine tonsils-in lateral walls of fauces
• Lingual tonsil-on posterior surface of
tongue
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Laryngopharynx
• Passageway for food and air
• Posterior to upright epiglottis
• Extends to larynx, where continuous with
esophagus
• Lined with stratified squamous epithelium
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Figure 22.3b The upper respiratory tract.
Cribriform plate
of ethmoid bone
Sphenoid sinus
Frontal sinus
Nasal cavity
Nasal conchae
(superior, middle
and inferior)
Nasal meatuses
(superior, middle,
and inferior)
Nasal vestibule
Posterior nasal
aperture
Nasopharynx
Pharyngeal tonsil
Opening of
pharyngotympanic tube
Uvula
Nostril
Oropharynx
Palatine tonsil
Isthmus of the
fauces
Hard palate
Soft palate
Tongue
Lingual tonsil
Laryngopharynx
Esophagus
Larynx
Epiglottis
Vestibular fold
Thyroid cartilage
Vocal fold
Cricoid cartilage
Trachea
Thyroid gland
Illustration
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Hyoid bone
Larynx
• Attaches to hyoid bone; opens into
laryngopharynx; continuous with trachea
• Functions
– Provides patent airway
– Routes air and food into proper channels
– Voice production
• Houses vocal folds
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Larynx
• Nine cartilages of larynx
– All hyaline cartilage except epiglottis
– Thyroid cartilage with laryngeal
prominence (Adam's apple)
– Ring-shaped cricoid cartilage
– Paired arytenoid, cuneiform, and
corniculate cartilages
– Epiglottis-elastic cartilage; covers laryngeal
inlet during swallowing; covered in taste budcontaining mucosa
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Figure 22.4a The larynx.
Epiglottis
Thyrohyoid
membrane
Body of hyoid bone
Thyroid cartilage
Laryngeal prominence
(Adam’s apple)
Cricothyroid ligament
Cricoid cartilage
Cricotracheal ligament
Tracheal cartilages
Anterior superficial view
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Figure 22.4b The larynx.
Epiglottis
Thyrohyoid
membrane
Body of hyoid bone
Thyrohyoid membrane
Cuneiform cartilage
Fatty pad
Corniculate cartilage
Vestibular fold
(false vocal cord)
Arytenoid cartilage
Thyroid cartilage
Arytenoid muscles
Vocal fold
(true vocal cord)
Cricoid cartilage
Cricothyroid ligament
Cricotracheal ligament
Tracheal cartilages
Sagittal view; anterior surface to the right
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Figure 22.4c The larynx.
Epiglottis
Hyoid bone
Thyroid
cartilage
Lateral
thyrohyoid
membrane
Corniculate
cartilage
Arytenoid
cartilage
Glottis
Cricoid
cartilage
Tracheal
cartilages
Photograph of cartilaginous framework
of the larynx, posterior view
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Figure 22.4d The larynx.
Epiglottis
Laryngeal
inlet
Corniculate
cartilage
Posterior
cricoarytenoid
muscle on
cricoid
cartilage
Trachea
(d) Photograph of posterior aspect
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Larynx
• Vocal ligaments-deep to laryngeal
mucosa
– Attach arytenoid cartilages to thyroid cartilage
– Contain elastic fibers
– Form core of vocal folds (true vocal cords)
• Glottis-opening between vocal folds
• Folds vibrate to produce sound as air rushes up
from lungs
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Larynx
• Vestibular folds (false vocal cords)
– Superior to vocal folds
– No part in sound production
– Help to close glottis during swallowing
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Figure 22.5 Movements of the vocal folds.
Base of tongue
Epiglottis
Vestibular fold (false vocal cord)
Vocal fold (true vocal cord)
Glottis
Inner lining of trachea
Cuneiform cartilage
Corniculate cartilage
Vocal folds in closed position; closed glottis
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Vocal folds in open position; open glottis
Epithelium of Larynx
• Superior portion–stratified squamous
epithelium
• Inferior to vocal folds–pseudostratified
ciliated columnar epithelium
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Voice Production
• Speech-intermittent release of expired air while
opening and closing glottis
• Pitch determined by length and tension of vocal
cords
• Loudness depends upon force of air
• Chambers of pharynx, oral, nasal, and sinus
cavities amplify and enhance sound quality
• Sound is "shaped" into language by muscles of
pharynx, tongue, soft palate, and lips
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Larynx
• Vocal folds may act as sphincter to
prevent air passage
• Example-Valsalva's maneuver
– Glottis closes to prevent exhalation
– Abdominal muscles contract
– Intra-abdominal pressure rises
– Helps to empty rectum or stabilizes trunk
during heavy lifting
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Trachea
• Windpipe–from larynx into mediastinum
• Wall composed of three layers
– Mucosa-ciliated pseudostratified epithelium
with goblet cells
– Submucosa-connective tissue with
seromucous glands
– Adventitia-outermost layer made of
connective tissue; encases 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
– Spar of cartilage on last, expanded tracheal
cartilage
– Point where trachea branches into two main
bronchi
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Figure 22.6a Tissue composition of the tracheal wall.
Posterior
Mucosa
Esophagus
Trachealis
muscle
Submucosa
Lumen of
trachea
Seromucous gland
in submucosa
Hyaline cartilage
Adventitia
Anterior
Cross section of the trachea
and esophagus
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Figure 22.6b Tissue composition of the tracheal wall.
Goblet cell
Mucosa
• Pseudostratified
ciliated columnar
epithelium
• Lamina propria
(connective tissue)
Submucosa
Seromucous gland
In submucosa
Hyaline cartilage
Photomicrograph of the tracheal
wall (320x)
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Figure 22.6c Tissue composition of the tracheal wall.
Scanning electron micrograph of cilia in the
trachea (2500x)
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Bronchi and Subdivisions
• Air passages undergo 23 orders of
branching  bronchial (respiratory) tree
• From tips of bronchial tree  conducting
zone structures  respiratory zone
structures
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Conducting Zone Structures
• Trachea  right and left main (primary)
bronchi
• Each main bronchus enters hilum of one
lung
– Right main bronchus wider, shorter, more
vertical than left
• Each main bronchus branches into lobar
(secondary) bronchi (three on right, two
on 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
• Branches become smaller and smaller 
– Bronchioles-less than 1 mm in diameter
– Terminal bronchioles-smallest-less than
0.5 mm diameter
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Figure 22.7 Conducting zone passages.
Trachea
Superior lobe
of left lung
Left main
(primary)
bronchus
Superior lobe
of right lung
Lobar (secondary)
bronchus
Segmental (tertiary)
bronchus
Middle lobe
of right lung
Inferior lobe
of right lung
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Inferior lobe
of left lung
Conducting Zone Structures
• From bronchi through bronchioles,
structural changes occur
– Cartilage rings become irregular plates; in
bronchioles elastic fibers replace cartilage
– Epithelium changes from pseudostratified
columnar to cuboidal; cilia and goblet cells
become sparse
– Relative amount of smooth muscle increases
• Allows constriction
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Respiratory Zone
• Begins as terminal bronchioles 
respiratory bronchioles  alveolar
ducts  alveolar sacs
– Alveolar sacs contain clusters of alveoli
• ~300 million alveoli make up most of lung volume
• Sites of gas exchange
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Figure 22.8a Respiratory zone structures.
Alveoli
Alveolar duct
Respiratory bronchioles
Terminal
bronchiole
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Alveolar duct
Alveolar
sac
Figure 22.8b Respiratory zone structures.
Respiratory
bronchiole
Alveolar
duct
Alveoli
Alveolar
sac
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Alveolar
pores
Respiratory Membrane
• Alveolar and capillary walls and their fused
basement membranes
– ~0.5- m-thick; gas exchange across
membrane by simple diffusion
• Alveolar walls
– Single layer of squamous epithelium (type I
alveolar cells)
• Scattered cuboidal type II alveolar cells
secrete surfactant and antimicrobial
proteins
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Figure 22.9a Alveoli and the respiratory membrane.
Terminal bronchiole
Respiratory bronchiole
Smooth
muscle
Elastic
fibers
Alveolus
Capillaries
Diagrammatic view of capillary-alveoli relationships
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Figure 22.9b Alveoli and the respiratory membrane.
Scanning electron micrograph of pulmonary capillary
casts (70x)
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Alveoli
• Surrounded by fine elastic fibers and
pulmonary capillaries
• Alveolar pores connect adjacent alveoli
• Equalize air pressure throughout lung
• Alveolar macrophages keep alveolar
surfaces sterile
– 2 million dead macrophages/hour carried by
cilia  throat  swallowed
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Figure 22.9c Alveoli and the respiratory membrane.
Red blood
cell
Nucleus of type I
alveolar cell
Alveolar pores
Capillary
Capillary
Macrophage
Endothelial cell
nucleus
Alveolus
Respiratory
membrane
Alveoli
(gas-filled
air spaces)
Red blood
cell in
capillary
Type II
alveolar
cell
Type I
alveolar
cell
Detailed anatomy of the respiratory membrane
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Alveolus
Alveolar
epithelium
Fused basement
membranes of
alveolar
epithelium and
capillary
endothelium
Capillary
endothelium
Lungs
• Occupy all thoracic cavity except
mediastinum
• Root-site of vascular and bronchial
attachment to mediastinum
• Costal surface-anterior, lateral, and
posterior surfaces
• Composed primarily of alveoli
• Balance–stroma-elastic connective tissue
 elasticity
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Figure 22.10c Anatomical relationships of organs in the thoracic cavity.
Vertebra
Right lung
Parietal pleura
Visceral pleura
Pleural cavity
Posterior
Esophagus
(in mediastinum)
Root of lung
at hilum
• Left main
bronchus
• Left pulmonary
artery
• Left pulmonary
vein
Left lung
Thoracic wall
Pulmonary trunk
Pericardial
membranes
Sternum
Heart (in mediastinum)
Anterior mediastinum
Anterior
Transverse section through the thorax, viewed from above. Lungs, pleural
membranes, and major organs in the mediastinum are shown.
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Lungs
• Apex-superior tip; deep to clavicle
• Base-inferior surface; rests on diaphragm
• Hilum-on mediastinal surface; site for
entry/exit of blood vessels, bronchi,
lymphatic vessels, and nerves
• Left lung smaller than right
– Cardiac notch-concavity for heart
– Separated into superior and inferior lobes by
oblique fissure
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Lungs
• Right lung
– Superior, middle, inferior lobes separated by
oblique and horizontal fissures
• Bronchopulmonary segments (10 right,
8–10 left) separated by connective tissue
septa
– If diseased can be individually removed
• Lobules-smallest subdivisions visible to
naked eye; served by bronchioles and
their branches
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Figure 22.10a Anatomical relationships of organs in the thoracic cavity.
Intercostal
muscle
Rib
Lung
Parietal pleura
Pleural cavity
Visceral pleura
Trachea
Thymus
Apex of lung
Left
superior lobe
Right superior lobe
Horizontal fissure
Right middle lobe
Oblique fissure
Oblique
fissure
Left inferior
lobe
Right inferior lobe
Heart
(in mediastinum)
Diaphragm
Cardiac notch
Base of lung
Anterior view. The lungs flank mediastinal structures laterally.
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Figure 22.10b Anatomical relationships of organs in the thoracic cavity.
Apex of lung
Pulmonary
artery
Left
superior lobe
Oblique
fissure
Pulmonary
vein
Left inferior
lobe
Cardiac
impression
Hilum of lung
Oblique
fissure
Aortic
impression
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Left main
bronchus
Lobules
Photograph of medial view of the
left lung.
Figure 22.11 A cast of the bronchial tree.
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)
Blood Supply
• Pulmonary circulation (low pressure,
high volume)
– Pulmonary arteries deliver systemic venous
blood to lungs for oxygenation
• Branch profusely; feed into pulmonary capillary
networks
– Pulmonary veins carry oxygenated blood
from respiratory zones to heart
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Blood Supply
– Lung capillary endothelium contains enzymes
that act on substances in blood
• E.g., angiotensin-converting enzyme–activates
blood pressure hormone
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Blood Supply
• Bronchial arteries provide oxygenated
blood to lung tissue
– Arise from aorta and enter lungs at hilum
– Part of systemic circulation (high pressure,
low volume)
– Supply all lung tissue except alveoli
– Bronchial veins anastomose with pulmonary
veins
• Pulmonary veins carry most venous blood back to
heart
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Pleurae
• Thin, double-layered serosa; divides
thoracic cavity into two pleural
compartments and mediastinum
• Parietal pleura on thoracic wall, superior
face of diaphragm, around heart, between
lungs
• Visceral pleura on external lung surface
• Pleural fluid fills slitlike pleural cavity
– Provides lubrication and surface tension 
assists in expansion and recoil
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Figure 22.10c Anatomical relationships of organs in the thoracic cavity.
Vertebra
Right lung
Parietal pleura
Visceral pleura
Pleural cavity
Posterior
Esophagus
(in mediastinum)
Root of lung
at hilum
• Left main
bronchus
• Left pulmonary
artery
• Left pulmonary
vein
Left lung
Thoracic wall
Pulmonary trunk
Pericardial
membranes
Sternum
Heart (in mediastinum)
Anterior mediastinum
Anterior
Transverse section through the thorax, viewed from above. Lungs, pleural
membranes, and major organs in the mediastinum are shown.
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Mechanics of Breathing
• Pulmonary ventilation consists of two
phases
– Inspiration-gases flow into lungs
– Expiration-gases exit lungs
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Pressure Relationships in the Thoracic
Cavity
• Atmospheric pressure (Patm)
– Pressure exerted by air surrounding body
– 760 mm Hg at sea level = 1 atmosphere
• Respiratory pressures described relative
to Patm
– Negative respiratory pressure-less than Patm
– Positive respiratory pressure-greater than Patm
– Zero respiratory pressure = Patm
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Intrapulmonary Pressure
• Intrapulmonary (intra-alveolar) pressure
(Ppul)
– Pressure in alveoli
– Fluctuates with breathing
– Always eventually equalizes with Patm
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Intrapleural Pressure
• Intrapleural pressure (Pip)
– Pressure in pleural cavity
– Fluctuates with breathing
– Always a negative pressure (<Patm and <Ppul)
– Fluid level must be minimal
• Pumped out by lymphatics
• If accumulates  positive Pip pressure  lung
collapse
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Intrapleural Pressure
• Negative Pip 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 lungs
• Elasticity of chest wall pulls thorax outward
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Pressure Relationships
• If Pip = Ppul or Patm  lungs collapse
• (Ppul – Pip) = transpulmonary pressure
– Keeps airways open
– Greater transpulmonary pressure  larger
lungs
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Figure 22.12 Intrapulmonary and intrapleural pressure relationships.
Atmospheric pressure (Patm)
0 mm Hg (760 mm Hg)
Parietal pleura
Thoracic wall
Visceral pleura
Pleural cavity
Transpulmonary
pressure
4 mm Hg
(the difference
between 0 mm Hg
and −4 mm Hg)
–4
0
Lung
Diaphragm
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Intrapulmonary
pressure (Ppul)
0 mm Hg
(760 mm Hg)
Intrapleural
pressure (Pip)
−4 mm Hg
(756 mm Hg)
Homeostatic Imbalance
• Atelectasis (lung collapse) due to
– Plugged bronchioles  collapse of alveoli
– Pneumothorax-air in pleural cavity
• From either wound in parietal or rupture of visceral
pleura
• Treated by removing air with chest tubes; pleurae
heal  lung reinflates
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Pulmonary Ventilation
• Inspiration and expiration
• Mechanical processes that depend on
volume changes in thoracic cavity
– Volume changes  pressure changes
– Pressure changes  gases flow to equalize
pressure
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Boyle's Law
• Relationship between pressure and
volume of a gas
– Gases fill container; if container size reduced
 increased pressure
• Pressure (P) varies inversely with volume
(V):
– P1V1 = P2V2
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Inspiration
• Active process
– Inspiratory muscles (diaphragm and external
intercostals) contract
– Thoracic volume increases  intrapulmonary
pressure drops (to 1 mm Hg)
– Lungs stretched and intrapulmonary volume
increases
– Air flows into lungs, down its pressure
gradient, until Ppul = Patm
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Forced Inspiration
• Vigorous exercise, COPD  accessory
muscles (scalenes, sternocleidomastoid,
pectoralis minor)  further increase in
thoracic cage size
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Figure 22.13 Changes in thoracic volume and sequence of events during inspiration and expiration. (1 of 2) Slide 1
Sequence of events
Changes in anterior-posterior and
superior-inferior dimensions
Changes in lateral dimensions
(superior view)
1 Inspiratory muscles
contract (diaphragm
descends; rib cage rises).
Inspiration
2 Thoracic cavity volume
increases.
3 Lungs are stretched;
intrapulmonary volume
increases.
Ribs are
elevated and
sternum
flares as
external
intercostals
contract.
External
intercostals
contract.
4 Intrapulmonary pressure
drops (to –1 mm Hg).
5 Air (gases) flows into
lungs down its pressure
gradient until intrapulmonary
pressure is 0 (equal to
atmospheric pressure).
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Diaphragm
moves inferiorly
during
contraction.
Figure 22.13 Changes in thoracic volume and sequence of events during inspiration and expiration. (1 of 2) Slide 2
Sequence of events
Changes in anterior-posterior and
superior-inferior dimensions
Changes in lateral dimensions
(superior view)
Inspiration
1 Inspiratory muscles
contract (diaphragm
descends; rib cage rises).
Ribs are
elevated and
sternum
flares as
external
intercostals
contract.
External
intercostals
contract.
Diaphragm
moves inferiorly
during
contraction.
© 2013 Pearson Education, Inc.
Figure 22.13 Changes in thoracic volume and sequence of events during inspiration and expiration. (1 of 2) Slide 3
Sequence of events
Changes in anterior-posterior and
superior-inferior dimensions
Changes in lateral dimensions
(superior view)
1 Inspiratory muscles
contract (diaphragm
descends; rib cage rises).
Inspiration
2 Thoracic cavity volume
increases.
Ribs are
elevated and
sternum
flares as
external
intercostals
contract.
External
intercostals
contract.
Diaphragm
moves inferiorly
during
contraction.
© 2013 Pearson Education, Inc.
Figure 22.13 Changes in thoracic volume and sequence of events during inspiration and expiration. (1 of 2) Slide 4
Sequence of events
Changes in anterior-posterior and
superior-inferior dimensions
Changes in lateral dimensions
(superior view)
1 Inspiratory muscles
contract (diaphragm
descends; rib cage rises).
Inspiration
2 Thoracic cavity volume
increases.
3 Lungs are stretched;
intrapulmonary volume
increases.
Ribs are
elevated and
sternum
flares as
external
intercostals
contract.
External
intercostals
contract.
Diaphragm
moves inferiorly
during
contraction.
© 2013 Pearson Education, Inc.
Figure 22.13 Changes in thoracic volume and sequence of events during inspiration and expiration. (1 of 2) Slide 5
Sequence of events
Changes in anterior-posterior and
superior-inferior dimensions
Changes in lateral dimensions
(superior view)
1 Inspiratory muscles
contract (diaphragm
descends; rib cage rises).
Inspiration
2 Thoracic cavity volume
increases.
3 Lungs are stretched;
intrapulmonary volume
increases.
Ribs are
elevated and
sternum
flares as
external
intercostals
contract.
External
intercostals
contract.
4 Intrapulmonary pressure
drops (to –1 mm Hg).
Diaphragm
moves inferiorly
during
contraction.
© 2013 Pearson Education, Inc.
Figure 22.13 Changes in thoracic volume and sequence of events during inspiration and expiration. (1 of 2) Slide 6
Sequence of events
Changes in anterior-posterior and
superior-inferior dimensions
Changes in lateral dimensions
(superior view)
1 Inspiratory muscles
contract (diaphragm
descends; rib cage rises).
Inspiration
2 Thoracic cavity volume
increases.
3 Lungs are stretched;
intrapulmonary volume
increases.
Ribs are
elevated and
sternum
flares as
external
intercostals
contract.
External
intercostals
contract.
4 Intrapulmonary pressure
drops (to –1 mm Hg).
5 Air (gases) flows into
lungs down its pressure
gradient until intrapulmonary
pressure is 0 (equal to
atmospheric pressure).
© 2013 Pearson Education, Inc.
Diaphragm
moves inferiorly
during
contraction.
Expiration
• Quiet expiration normally passive process
– Inspiratory muscles relax
– Thoracic cavity volume decreases
– Elastic lungs recoil and intrapulmonary
volume decreases  pressure increases (Ppul
rises to +1 mm Hg) 
– Air flows out of lungs down its pressure
gradient until Ppul = 0
• Note: forced expiration-active process;
uses abdominal (oblique and transverse)
and internal intercostal muscles
© 2013 Pearson Education, Inc.
Figure 22.13 Changes in thoracic volume and sequence of events during inspiration and expiration. (2 of 2) Slide 1
Sequence of events
Changes in anterior-posterior and
superior-inferior dimensions
Changes in lateral dimensions
(superior view)
1 Inspiratory muscles relax
(diaphragm rises; rib cage
descends due to recoil of
costal cartilages).
Expiration
2 Thoracic cavity volume
decreases.
3 Elastic lungs recoil
passively; intrapulmonary
Volume decreases.
Ribs and
sternum are
depressed
as external
intercostals
relax.
External
intercostals
relax.
4 Intrapulmonary pressure
rises (to +1 mm Hg).
5 Air (gases) flows out of
lungs down its pressure
gradient until intrapulmonary
pressure is 0.
© 2013 Pearson Education, Inc.
Diaphragm
moves
superiorly
as it relaxes.
Figure 22.13 Changes in thoracic volume and sequence of events during inspiration and expiration. (2 of 2) Slide 2
Sequence of events
Changes in anterior-posterior and
superior-inferior dimensions
Changes in lateral dimensions
(superior view)
Expiration
1 Inspiratory muscles relax
(diaphragm rises; rib cage
descends due to recoil of
costal cartilages).
Ribs and
sternum are
depressed
as external
intercostals
relax.
External
intercostals
relax.
Diaphragm
moves
superiorly
as it relaxes.
© 2013 Pearson Education, Inc.
Figure 22.13 Changes in thoracic volume and sequence of events during inspiration and expiration. (2 of 2) Slide 3
Sequence of events
Changes in anterior-posterior and
superior-inferior dimensions
Changes in lateral dimensions
(superior view)
1 Inspiratory muscles relax
(diaphragm rises; rib cage
descends due to recoil of
costal cartilages).
Expiration
2 Thoracic cavity volume
decreases.
Ribs and
sternum are
depressed
as external
intercostals
relax.
External
intercostals
relax.
Diaphragm
moves
superiorly
as it relaxes.
© 2013 Pearson Education, Inc.
Figure 22.13 Changes in thoracic volume and sequence of events during inspiration and expiration. (2 of 2) Slide 4
Sequence of events
Changes in anterior-posterior and
superior-inferior dimensions
Changes in lateral dimensions
(superior view)
1 Inspiratory muscles relax
(diaphragm rises; rib cage
descends due to recoil of
costal cartilages).
Expiration
2 Thoracic cavity volume
decreases.
3 Elastic lungs recoil
passively; intrapulmonary
Volume decreases.
Ribs and
sternum are
depressed
as external
intercostals
relax.
External
intercostals
relax.
Diaphragm
moves
superiorly
as it relaxes.
© 2013 Pearson Education, Inc.
Figure 22.13 Changes in thoracic volume and sequence of events during inspiration and expiration. (2 of 2) Slide 5
Sequence of events
Changes in anterior-posterior and
superior-inferior dimensions
Changes in lateral dimensions
(superior view)
1 Inspiratory muscles relax
(diaphragm rises; rib cage
descends due to recoil of
costal cartilages).
Expiration
2 Thoracic cavity volume
decreases.
3 Elastic lungs recoil
passively; intrapulmonary
Volume decreases.
Ribs and
sternum are
depressed
as external
intercostals
relax.
External
intercostals
relax.
4 Intrapulmonary pressure
rises (to +1 mm Hg).
Diaphragm
moves
superiorly
as it relaxes.
© 2013 Pearson Education, Inc.
Figure 22.13 Changes in thoracic volume and sequence of events during inspiration and expiration. (2 of 2) Slide 6
Sequence of events
Changes in anterior-posterior and
superior-inferior dimensions
Changes in lateral dimensions
(superior view)
1 Inspiratory muscles relax
(diaphragm rises; rib cage
descends due to recoil of
costal cartilages).
Expiration
2 Thoracic cavity volume
decreases.
3 Elastic lungs recoil
passively; intrapulmonary
Volume decreases.
Ribs and
sternum are
depressed
as external
intercostals
relax.
External
intercostals
relax.
4 Intrapulmonary pressure
rises (to +1 mm Hg).
5 Air (gases) flows out of
lungs down its pressure
gradient until intrapulmonary
pressure is 0.
© 2013 Pearson Education, Inc.
Diaphragm
moves
superiorly
as it relaxes.
Intrapleural pressure.
Pleural cavity pressure
becomes more negative as
chest wall expands during
inspiration. Returns to initial
value as chest wall recoils.
Volume of breath. During
each breath, the pressure
gradients move 0.5 liter of
air into and out of the lungs.
Volume (L)
Intrapulmonary pressure.
Pressure inside lung
decreases as lung volume
increases during
inspiration; pressure
increases during expiration.
Pressure relative to
atmospheric pressure (mm Hg)
Figure 22.14 Changes in intrapulmonary and intrapleural pressures during inspiration and expiration.
Inspiration
Expiration
Intrapulmonary
pressure
+2
0
–2
–4
Transpulmonary
pressure
–6
Intrapleural
pressure
–8
Volume of breath
0.5
0
5 seconds elapsed
© 2013 Pearson Education, Inc.
Physical Factors Influencing Pulmonary
Ventilation
• Three factors hinder air passage and
pulmonary ventilation; require energy to
overcome
– Airway resistance
– Alveolar surface tension
– Lung compliance
© 2013 Pearson Education, Inc.
Airway Resistance
• Friction-major nonelastic source of
resistance to gas flow; occurs in airways
• Relationship between flow (F), pressure
(P), and resistance (R) is:
– ∆P - pressure gradient between atmosphere
and alveoli (2 mm Hg or less during normal
quiet breathing)
– Gas flow changes inversely with resistance
© 2013 Pearson Education, Inc.
Airway Resistance
• Resistance usually insignificant
– Large airway diameters in first part of
conducting zone
– Progressive branching of airways as get
smaller, increasing total cross-sectional area
– Resistance greatest in medium-sized bronchi
• Resistance disappears at terminal
bronchioles where diffusion drives gas
movement
© 2013 Pearson Education, Inc.
Figure 22.15 Resistance in respiratory passageways.
Conducting
zone
Respiratory
zone
Resistance
Medium-sized
bronchi
Terminal
bronchioles
1
© 2013 Pearson Education, Inc.
5
10
15
Airway generation
(stage of branching)
20
23
Homeostatic Imbalance
• As airway resistance rises, breathing
movements become more strenuous
• Severe constriction or obstruction of
bronchioles
– Can prevent life-sustaining ventilation
– Can occur during acute asthma attacks; stops
ventilation
• Epinephrine dilates bronchioles, reduces
air resistance
© 2013 Pearson Education, Inc.
Alveolar Surface Tension
• Surface tension
– Attracts liquid molecules to one another at
gas-liquid interface
– Resists any force that tends to increase
surface area of liquid
– Water–high surface tension; coats alveolar
walls  reduces them to smallest size
© 2013 Pearson Education, Inc.
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
•  alveoli collapse after each breath
© 2013 Pearson Education, Inc.
Lung Compliance
• Measure of change in lung volume that
occurs with given change in
transpulmonary pressure
• Higher lung compliance  easier to
expand lungs
• Normally high due to
– Distensibility of lung tissue
– Alveolar surface tension
© 2013 Pearson Education, Inc.
Lung Compliance
• Diminished by
– Nonelastic scar tissue replacing lung tissue
(fibrosis)
– Reduced production of surfactant
– Decreased flexibility of thoracic cage
© 2013 Pearson Education, Inc.
Lung Compliance
• Homeostatic imbalances that reduce
compliance
– Deformities of thorax
– Ossification of costal cartilage
– Paralysis of intercostal muscles
© 2013 Pearson Education, Inc.