Transcript APII_ch_23_lecture_presentationx

Chapter 23
The Respiratory
System
Lecture Presentation by
Lee Ann Frederick
University of Texas at Arlington
© 2015 Pearson Education, Inc.
The Respiratory System
• Learning Outcomes
• 23-1 Describe the primary functions of the
respiratory system, and explain how the
delicate respiratory exchange surfaces are
protected from pathogens, debris, and other
hazards.
• 23-2 Identify the organs of the upper respiratory
system, and describe their functions.
• 23-3 Describe the structure of the larynx, and
discuss its roles in normal breathing and in
sound production.
© 2015 Pearson Education, Inc.
The Respiratory System
• Learning Outcomes
• 23-4 Discuss the structure of the extrapulmonary
airways.
• 23-5 Describe the superficial anatomy of the
lungs, the structure of a pulmonary lobule,
and the functional anatomy of alveoli.
• 23-6 Define and compare the processes of
external respiration and internal respiration.
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The Respiratory System
• Learning Outcomes
• 23-7 Summarize the physical principles controlling
the movement of air into and out of the
lungs, and describe the origins and actions
of the muscles responsible for respiratory
movements.
• 23-8 Summarize the physical principles governing
the diffusion of gases into and out of the
blood and body tissues.
• 23-9 Describe the structure and function of
hemoglobin, and the transport of oxygen
and carbon dioxide in the blood.
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The Respiratory System
• Learning Outcomes
• 23-10 List the factors that influence respiration
rate, and discuss reflex respiratory activity
and the brain centers involved in the
control of respiration.
• 23-11 Describe age-related changes in the
respiratory system.
• 23-12 Give examples of interactions between the
respiratory system and other organ
systems studied so far.
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An Introduction to the Respiratory System
• The Respiratory System
• Cells produce energy
• For maintenance, growth, defense, and division
• Through mechanisms that use oxygen and produce
carbon dioxide
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An Introduction to the Respiratory System
• Oxygen
• Is obtained from the air by diffusion across
delicate exchange surfaces of lungs
• Is carried to cells by the cardiovascular system,
which also returns carbon dioxide to the lungs
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23-1 Components of the Respiratory System
• Five Functions of the Respiratory System
1. Provides extensive gas exchange surface area
between air and circulating blood
2. Moves air to and from exchange surfaces of
lungs
3. Protects respiratory surfaces from outside
environment
4. Produces sounds
5. Participates in olfactory sense
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23-1 Components of the Respiratory System
• Organization of the Respiratory System
• The respiratory system is divided into:
• Upper respiratory system – above the larynx
• Lower respiratory system – below the larynx
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23-1 Components of the Respiratory System
• The Respiratory Tract
• Consists of a conducting portion
• From nasal cavity to terminal bronchioles
• Consists of a respiratory portion
• The respiratory bronchioles and alveoli
• Alveoli
• Are air-filled pockets within the lungs
• Where all gas exchange takes place
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Figure 23-1 The Structures of the Respiratory System.
Upper Respiratory System
Nose
Nasal cavity
Sinuses
Tongue
Pharynx
Esophagus
Lower Respiratory System
Clavicle
Larynx
Trachea
Bronchus
Bronchioles
Smallest bronchioles
Ribs
Right
lung
Left
lung
Alveoli
Diaphragm
© 2015 Pearson Education, Inc.
23-1 Components of the Respiratory System
• The Respiratory Epithelium
• For gases to exchange efficiently:
• Alveoli walls must be very thin (<1 µm)
• Surface area must be very great (about 35 times
the surface area of the body)
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23-1 Components of the Respiratory System
• The Respiratory Mucosa
• Consists of:
• An epithelial layer
• An areolar layer called the lamina propria
• Lines the conducting portion of respiratory system
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23-1 Components of the Respiratory System
• The Lamina Propria
• Underlying layer of areolar tissue that supports the
respiratory epithelium
• In the upper respiratory system, trachea, and
bronchi
• It contains mucous glands that secrete onto
epithelial surface
• In the conducting portion of lower respiratory
system
• It contains smooth muscle cells that encircle lumen
of bronchioles
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Figure 23-2a The Respiratory Epithelium of the Nasal Cavity and Conducting System.
Superficial view
SEM × 1647
a A surface view of the epithelium. The cilia of
the epithelial cells form a dense layer that
resembles a shag carpet. The movement of
these cilia propels mucus across the
epithelial surface.
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Figure 23-2b The Respiratory Epithelium of the Nasal Cavity and Conducting System.
Movement
of mucus
to pharynx
Ciliated columnar
epithelial cell
Mucous cell
Stem cell
Mucus layer
Lamina propria
b A diagrammatic view of the respiratory
epithelium of the trachea, showing the direction
of mucus transport inferior to the pharynx.
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Figure 23-2c The Respiratory Epithelium of the Nasal Cavity and Conducting System.
Cilia
Lamina
propria
Nucleus of
columnar
epithelial cell
Mucous cell
Basement
membrane
Stem cell
c A sectional view of the respiratory epithelium, a
pseudostratified ciliated columnar epithelium.
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23-1 Components of the Respiratory System
• Structure of Respiratory Epithelium
• Pseudostratified ciliated columnar epithelium with
numerous mucous cells
• Nasal cavity and superior portion of the pharynx
• Stratified squamous epithelium
• Inferior portions of the pharynx
• Pseudostratified ciliated columnar epithelium
• Superior portion of the lower respiratory system
• Cuboidal epithelium with scattered cilia
• Smaller bronchioles
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23-1 Components of the Respiratory System
• Alveolar Epithelium
• Is a very delicate, simple squamous epithelium
• Contains scattered and specialized cells
• Lines exchange surfaces of alveoli
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23-1 Components of the Respiratory System
• The Respiratory Defense System
• Consists of a series of filtration mechanisms
• Removes particles and pathogens
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23-1 Components of the Respiratory System
• Components of the Respiratory Defense System
• Mucous cells and mucous glands
• Produce mucus that bathes exposed surfaces
• Cilia
• Sweep debris trapped in mucus toward the pharynx
(mucus escalator)
• Filtration in nasal cavity removes large particles
• Alveolar macrophages engulf small particles that
reach lungs
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23-2 Upper Respiratory Tract
• 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
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23-2 Upper Respiratory Tract
• The Nasal Cavity
• The nasal septum
• Divides nasal cavity into left and right
• Superior portion of nasal cavity is the olfactory
region
• Provides sense of smell
• Mucous secretions from paranasal sinus and tears
• Clean and moisten the nasal cavity
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23-2 Upper Respiratory Tract
• Air Flow
• From vestibule to internal nares
• Through superior, middle, and inferior meatuses
• Meatuses are constricted passageways that
produce air turbulence
• Warm and humidify incoming air
• Trap particles
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23-2 Upper Respiratory Tract
• 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
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23-2 Upper Respiratory Tract
• Air Flow
• Nasal cavity opens into nasopharynx through
internal nares
• The Nasal Mucosa
• Warms and humidifies inhaled air for arrival at
lower respiratory organs
• Breathing through mouth bypasses this important
step
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Figure 23-3a The Structures of the Upper Respiratory System.
Dorsum
nasi
Apex
Nasal
cartilages
External
nares
a The nasal cartilages and external
landmarks on the nose
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Figure 23-3b The Structures of the Upper Respiratory System.
Ethmoidal
air cell
Medial rectus
muscle
Cranial cavity
Frontal sinus
Right eye
Lens
Lateral rectus
muscle
Nasal septum
Perpendicular
plate of ethmoid
Vomer
Hard palate
Superior
nasal concha
Superior
meatus
Middle nasal
concha
Middle meatus
Maxillary sinus
Inferior nasal
concha
Inferior meatus
Tongue
Mandible
b A frontal section through the head, showing the
meatuses and the maxillary sinuses and air cells
of the ethmoidal labyrinth
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Figure 23-3c The Structures of the Upper Respiratory System (Part 2 of 2).
Frontal sinus
Nasal conchae
Nasal cavity
Superior
Middle
Internal nares
Inferior
Nasopharyngeal meatus
Nasal vestibule
Pharyngeal tonsil
Pharynx
External nares
Hard palate
Oral cavity
Nasopharynx
Oropharynx
Laryngopharynx
Tongue
Soft palate
Palatine tonsil
Mandible
Epiglottis
Lingual tonsil
Hyoid bone
Glottis
Thyroid cartilage
Cricoid cartilage
Trachea
Esophagus
Thyroid gland
c The nasal cavity and pharynx, as seen in sagittal section with the
nasal septum removed
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23-2 Upper Respiratory Tract
• The Pharynx
• A chamber shared by digestive and respiratory
systems
• Extends from internal nares to entrances to larynx
and esophagus
• Divided into three parts
1. The nasopharynx
2. The oropharynx
3. The laryngopharynx
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23-2 Upper Respiratory Tract
• The Nasopharynx
• Superior portion of pharynx
• Contains pharyngeal tonsils and openings to left
and right auditory tubes
• The Oropharynx
• Middle portion of pharynx
• Communicates with oral cavity
• The Laryngopharynx
• Inferior portion of pharynx
• Extends from hyoid bone to entrance of larynx and
esophagus
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23-3 The Larynx
• Air Flow
• From the pharynx enters the larynx
• A cartilaginous structure that surrounds the glottis,
which is a narrow opening
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23-3 The Larynx
• Cartilages of the Larynx
• Three large, unpaired cartilages form the larynx
1. Thyroid cartilage
2. Cricoid cartilage
3. Epiglottis
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23-3 The Larynx
• The Thyroid Cartilage
• Is hyaline cartilage
• Forms anterior and lateral walls of larynx
• Anterior surface called laryngeal prominence, or
Adam’s apple
• Ligaments attach to hyoid bone, epiglottis, and
laryngeal cartilages
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23-3 The Larynx
• The Cricoid Cartilage
•
•
•
•
Is hyaline cartilage
Forms posterior portion of larynx
Ligaments attach to first tracheal cartilage
Articulates with arytenoid cartilages
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23-3 The Larynx
• The Epiglottis
• Composed of elastic cartilage
• Ligaments attach to thyroid cartilage and hyoid
bone
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23-3 The Larynx
• Cartilage Functions
• Thyroid and cricoid cartilages support and protect:
• The glottis
• The entrance to trachea
• During swallowing:
• The larynx is elevated
• The epiglottis folds back over glottis
• Prevents entry of food and liquids into respiratory
tract
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23-3 The Larynx
• The Larynx Contains Three Pairs of Smaller
Hyaline Cartilages
1. Arytenoid cartilages
2. Corniculate cartilages
3. Cuneiform cartilages
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Figure 23-4a The Anatomy of the Larynx.
Epiglottis
Lesser cornu
Hyoid bone
Thyrohyoid
ligament
Laryngeal
prominence
Thyroid
cartilage
Larynx
Cricothyroid
ligament
Cricoid cartilage
Cricotracheal
ligament
Trachea
Tracheal
cartilages
a
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Anterior view
Figure 23-4b The Anatomy of the Larynx.
Epiglottis
Vestibular
ligament
Corniculate
cartilage
Vocal ligament
Thyroid
cartilage
Arytenoid
cartilage
Cricoid cartilage
Tracheal
cartilages
b
© 2015 Pearson Education, Inc.
Posterior view
Figure 23-4c The Anatomy of the Larynx.
Hyoid bone
Epiglottis
Thyroid
cartilage
Vestibular
ligament
Corniculate
cartilage
Vocal ligament
Arytenoid
cartilage
Cricoid
cartilage
Cricothyroid ligament
Tracheal
cartilages
Cricotracheal ligament
ANTERIOR
POSTERIOR
c
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Sagittal section
23-3 The Larynx
• Cartilage Functions
• Corniculate and arytenoid cartilages function in:
• Opening and closing of glottis
• Production of sound
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23-3 The Larynx
• Ligaments of the Larynx
• Vestibular ligaments and vocal ligaments
• Extend between thyroid cartilage and arytenoid
cartilages
• Are covered by folds of laryngeal epithelium that
project into glottis
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23-3 The Larynx
• The Vestibular Ligaments
• Lie within vestibular folds
• Which protect delicate vocal folds
• Sound Production
• Air passing through glottis
• Vibrates vocal folds
• Produces sound waves
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23-3 The Larynx
• Sound Production
• Sound is varied by:
• Tension on vocal folds
• Vocal folds involved with sound are known as vocal
cords
• Voluntary muscles (position arytenoid cartilage
relative to thyroid cartilage)
• Speech is produced by:
• Phonation
• Sound production at the larynx
• Articulation
• Modification of sound by other structures
© 2015 Pearson Education, Inc.
Figure 23-5a The Glottis and Surrounding Structures.
Corniculate
cartilage
POSTERIOR
Cuneiform
cartilage
Aryepiglottic
fold
Vestibular
fold
Vocal fold
of glottis
Epiglottis
Root of tongue
ANTERIOR
a
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Glottis in the closed position.
Figure 23-5b The Glottis and Surrounding Structures.
POSTERIOR
Corniculate cartilage
Cuneiform cartilage
Glottis (open)
Rima glottidis
Vocal fold
Vestibular fold
Epiglottis
ANTERIOR
b
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Glottis in the open position.
Figure 23-5c The Glottis and Surrounding Structures.
Corniculate cartilage
Cuneiform cartilage
Glottis (open)
Rima glottidis
Vocal fold
Vestibular fold
Vocal nodule
Epiglottis
c Photograph taken with a laryngoscope
positioned within the oropharynx,
superior to the larynx. Note the
abnormal vocal nodule.
© 2015 Pearson Education, Inc.
23-3 The Larynx
• The Laryngeal Musculature
• The larynx is associated with:
1. Muscles of neck and pharynx
2. Intrinsic muscles
• Control vocal folds
• Open and close glottis
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23-4 The Trachea
• The Trachea
• Also called the windpipe
• Extends from the cricoid cartilage into
mediastinum
• Where it branches into right and left pulmonary
bronchi
• The submucosa
• Beneath mucosa of trachea
• Contains mucous glands
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Figure 23-6b The Anatomy of the Trachea.
Esophagus
Trachealis
muscle
Thyroid
gland
Lumen of
trachea
Respiratory
epithelium
Tracheal
cartilage
The trachea
b A cross-sectional view
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LM × 3
23-4 The Trachea
• 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
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23-4 The Trachea
• 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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Figure 23-6a The Anatomy of the Trachea.
Hyoid
bone
Larynx
Trachea
Tracheal
cartilages
Location of carina
(internal ridge)
Root of
right lung
Lung
tissue
RIGHT LUNG
a
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Root of
left lung
Primary
bronchi
Secondary
bronchi
LEFT LUNG
A diagrammatic anterior view showing the plane of section
for part (b)
23-4 The Trachea
• The Primary Bronchi
• Hilum
• Where pulmonary nerves, blood vessels,
lymphatics enter lung
• Anchored in meshwork of connective tissue
• The root of the lung
• Complex of connective tissues, nerves, and
vessels in hilum
• Anchored to the mediastinum
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23-5 The Lungs
• 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
• Lobes of the lungs
• Lungs have lobes separated by deep fissures
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23-5 The Lungs
• Lobes and Surfaces of the Lungs
• The right lung has three lobes
• Superior, middle, and inferior
• Separated by horizontal and oblique fissures
• The left lung has two lobes
• Superior and inferior
• Separated by an oblique fissure
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23-5 The Lungs
• Lung Shape
• Right lung
• Is wider
• Is displaced upward by liver
• Left lung
• Is longer
• Is displaced leftward by the heart forming the
cardiac notch
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Figure 23-7a The Gross Anatomy of the Lungs (Part 2 of 2).
Boundary between
right and left
pleural cavities
Superior lobe
Left lung
Right lung
Superior lobe
Oblique fissure
Horizontal fissure
Middle lobe
Fibrous layer
of pericardium
Inferior lobe
Oblique fissure
Inferior lobe
Falciform ligament
Liver,
right lobe
Liver,
left lobe
a Thoracic cavity, anterior view
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Cut edge of
diaphragm
Figure 23-7b The Gross Anatomy of the Lungs.
b
Lateral Surfaces
The curving anterior and lateral
surfaces of each lung follow the
inner contours of the rib cage.
Apex
Apex
Superior
lobe
ANTERIOR
Superior lobe
Horizontal fissure
Middle
lobe
Oblique fissure
Inferior
lobe
The cardiac notch
accommodates the
pericardial cavity,
which sits to the left
of the midline.
Oblique
fissure
Inferior
lobe
Base
Right lung
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Base
Left lung
Figure 23-7c The Gross Anatomy of the Lungs.
c
Medial Surfaces
The medial surfaces, which contain the
hilum, have more irregular shapes. The
medial surfaces of both lungs have grooves
that mark the positions of the great
vessels of the heart.
Apex
Superior
lobe
Pulmonary artery
Horizontal fissure
Middle
lobe
POSTERIOR
Inferior
lobe
Right lung
Groove
for aorta
Pulmonary
artery
Pulmonary
veins
Inferior
lobe
Oblique
fissure
Bronchus
Base
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Superior
lobe
Bronchus
The hilum of the lung is
a groove that allows
passage of the primary
bronchi, pulmonary
vessels, nerves, and
lymphatics.
Pulmonary veins
Oblique fissure
Apex
Diaphragmatic
surface
Base
Left lung
Figure 23-8 The Relationship between the Lungs and Heart (Part 2 of 2).
Pericardial
cavity
Right lung,
middle lobe
Oblique fissure
Right pleural
cavity
Atria
Esophagus
Aorta
Right lung,
inferior lobe
Spinal cord
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Body of sternum
Ventricles
Rib
Left lung,
superior lobe
Visceral pleura
Left pleural cavity
Parietal pleura
Bronchi
Mediastinum
Left lung,
inferior lobe
23-5 The Lungs
• The Bronchi
• The Bronchial Tree
• Is formed by the primary bronchi and their
branches
• Extrapulmonary Bronchi
• The left and right bronchi branches outside the
lungs
• Intrapulmonary Bronchi
• Branches within the lungs
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23-5 The Lungs
• A Primary Bronchus
• Branches to form secondary bronchi (lobar
bronchi)
• One secondary bronchus goes to each lobe
• Secondary Bronchi
• Branch to form tertiary bronchi (segmental
bronchi)
• Each segmental bronchus
• Supplies air to a single bronchopulmonary
segment
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23-5 The Lungs
• Bronchopulmonary Segments
• The right lung has 10
• The left lung has 8 or 9
• Bronchial Structure
• The walls of primary, secondary, and tertiary
bronchi
• Contain progressively less cartilage and more
smooth muscle
• Increased smooth muscle tension affects airway
constriction and resistance
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23-5 The Lungs
• Bronchitis
• Inflammation of bronchial walls
• Causes constriction and breathing difficulty
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23-5 The Lungs
• The Bronchioles
• Each tertiary bronchus branches into multiple
bronchioles
• Bronchioles branch into terminal bronchioles
• One tertiary bronchus forms about 6500 terminal
bronchioles
• Bronchiole Structure
• Bronchioles
• Have no cartilage
• Are dominated by smooth muscle
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23-5 The Lungs
• Autonomic Control
• Regulates smooth muscle
• Controls diameter of bronchioles
• Controls airflow and resistance in lungs
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23-5 The Lungs
• Bronchodilation
• Dilation of bronchial airways
• Caused by sympathetic ANS activation
• Reduces resistance
• Bronchoconstriction
• Constricts bronchi
• Caused by:
• Parasympathetic ANS activation
• Histamine release (allergic reactions)
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23-5 The Lungs
• Asthma
• Excessive stimulation and bronchoconstriction
• Stimulation severely restricts airflow
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23-5 The Lungs
• Pulmonary Lobules
• Trabeculae
• Fibrous connective tissue partitions from root of
lung
• Contain supportive tissues and lymphatic vessels
• Branch repeatedly
• Divide lobes into increasingly smaller
compartments
• Pulmonary lobules are divided by the smallest
trabecular partitions (interlobular septa)
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Figure 23-9a The Bronchi, Lobules, and Alveoli of the Lung.
LEFT
RIGHT
Bronchopulmonary
segments of
superior lobe
(3 segments)
Bronchopulmonary
segments of
superior lobe
(4 segments)
Bronchopulmonary
segments of
inferior lobe
(5 segments)
Bronchopulmonary
segments of
middle lobe
(2 segments)
Bronchopulmonary
segments of
inferior lobe
(5 segments)
a Anterior view of the lungs, showing
the bronchial tree and its divisions
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Figure 23-9b The Bronchi, Lobules, and Alveoli of the Lung.
Trachea
Cartilage
plates
Left primary
bronchus
Visceral pleura
Secondary
bronchus
Tertiary bronchi
Smaller
bronchi
Bronchioles
Terminal
bronchiole
Alveoli in a
pulmonary
lobule
Respiratory
bronchiole
Bronchopulmonary segment
b The branching pattern of bronchi
in the left lung, simplified
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Figure 23-9c The Bronchi, Lobules, and Alveoli of the Lung.
Respiratory epithelium
Bronchiole
Bronchial artery (red),
vein (blue), and
nerve (yellow)
Branch of pulmonary
artery
Smooth muscle
around terminal
bronchiole
Terminal bronchiole
Branch of
pulmonary
vein
Respiratory
bronchiole
Elastic fibers
around alveoli
Arteriole
Capillary
beds
Alveolar
duct
Lymphatic
vessel
Alveoli
Alveolar sac
Interlobular
septum
c The structure of a single pulmonary lobule,
part of a bronchopulmonary segment
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Figure 23-9d The Bronchi, Lobules, and Alveoli of the Lung.
Alveoli
Alveolar sac
Alveolar duct
Lung tissue
SEM × 125
d SEM of lung tissue showing the
appearance and organization of
the alveoli
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23-5 The Lungs
• Pulmonary Lobules
• Each terminal bronchiole delivers air to a single
pulmonary lobule
• Each pulmonary lobule is supplied by pulmonary
arteries and veins
• Each terminal bronchiole branches to form several
respiratory bronchioles, where gas exchange
takes place
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23-5 The Lungs
• Alveolar Ducts and Alveoli
• Respiratory bronchioles are connected to alveoli
along alveolar ducts
• Alveolar ducts end at alveolar sacs
• Common chambers connected to many individual
alveoli
• Each alveolus has an extensive network of
capillaries
• Surrounded by elastic fibers
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Figure 23-10a Alveolar Organization.
Respiratory bronchiole
Smooth
muscle
Elastic
fibers
Capillaries
a The basic structure of the distal end of a single
lobule. A network of capillaries, supported by
elastic fibers, surrounds each alveolus. Respiratory
bronchioles are also wrapped by smooth muscle
cells that can change the diameter of these airways.
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Alveolar duct
Alveolus
Alveolar
sac
Figure 23-10b Alveolar Organization.
Alveoli
Respiratory
bronchiole
Alveolar
sac
Arteriole
Histology of the lung
b Low-power micrograph of lung tissue.
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LM × 14
23-5 The Lungs
• Alveolar Epithelium
• Consists of simple squamous epithelium
• Consists of thin, delicate type I pneumocytes
patrolled by alveolar macrophages (dust cells)
• Contains type II pneumocytes (septal cells) that
produce surfactant
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23-5 The Lungs
• Surfactant
• Is an oily secretion
• Contains phospholipids and proteins
• Coats alveolar surfaces and reduces surface
tension
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Figure 23-10c Alveolar Organization.
Type II
pneumocyte
Type I pneumocyte
Alveolar
macrophage
Elastic
fibers
Alveolar macrophage
Capillary
Endothelial
cell of capillary
c A diagrammatic view of alveolar structure. A single capillary may be
involved in gas exchange with several alveoli simultaneously.
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23-5 The Lungs
• Respiratory Distress Syndrome
• Difficult respiration
• Due to alveolar collapse
• Caused when type II pneumocytes do not produce
enough surfactant
• Respiratory Membrane
• The thin membrane of alveoli where gas exchange
takes place
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23-5 The Lungs
• Three Layers of the Respiratory Membrane
1. Squamous epithelial cells lining the alveolus
2. Endothelial cells lining an adjacent capillary
3. Fused basement membranes between the
alveolar and endothelial cells
© 2015 Pearson Education, Inc.
Figure 23-10d Alveolar Organization.
Red blood cell
Capillary lumen
Capillary
endothelium
Nucleus of
endothelial cell
0.5 μm
Fused
Alveolar Surfactant
basement epithelium
membranes
Alveolar air space
d
© 2015 Pearson Education, Inc.
The respiratory membrane, which
consists of an alveolar epithelial cell,
a capillary endothelial cell, and their
fused basement membranes.
23-5 The Lungs
• Diffusion
• Across respiratory membrane is very rapid
• Because distance is short
• Gases (O2 and CO2) are lipid soluble
• Inflammation of Lobules
• Also called pneumonia
• Causes fluid to leak into alveoli
• Compromises function of respiratory membrane
© 2015 Pearson Education, Inc.
23-5 The Lungs
• Blood Supply to the Lungs
• Respiratory exchange surfaces receive blood
• From arteries of pulmonary circuit
• A capillary network surrounds each alveolus
• As part of the respiratory membrane
• Blood from alveolar capillaries
• Passes through pulmonary venules and veins
• Returns to left atrium
• Also site of angiotensin-converting enzyme (ACE)
© 2015 Pearson Education, Inc.
23-5 The Lungs
• Blood Supply to the Lungs
• Capillaries supplied by bronchial arteries
• Provide oxygen and nutrients to tissues of
conducting passageways of lung
• Venous blood bypasses the systemic circuit and
flows into pulmonary veins
© 2015 Pearson Education, Inc.
23-5 The Lungs
• Blood Pressure
• In pulmonary circuit is low (30 mm Hg)
• Pulmonary vessels are easily blocked by blood
clots, fat, or air bubbles
• Causing pulmonary embolism
© 2015 Pearson Education, Inc.
23-5 The Lungs
• The Pleural Cavities and Pleural Membranes
• Two pleural cavities
• Are separated by the mediastinum
• Each pleural cavity:
• Holds a lung
• Is lined with a serous membrane (the pleura)
© 2015 Pearson Education, Inc.
23-5 The Lungs
• The Pleura
• Consists of two layers
1. Parietal pleura
2. Visceral pleura
• Pleural fluid
• Lubricates space between two layers
© 2015 Pearson Education, Inc.
23-6 Introduction to Gas Exchange
• Respiration
• Refers to two integrated processes
1. External respiration
• Includes all processes involved in exchanging O2
and CO2 with the environment
2. Internal respiration
• Result of cellular respiration
• Involves the uptake of O2 and production of CO2
within individual cells
© 2015 Pearson Education, Inc.
23-6 Introduction to Gas Exchange
• Three Processes of External Respiration
1. Pulmonary ventilation (breathing)
2. Gas diffusion
• Across membranes and capillaries
3. Transport of O2 and CO2
• Between alveolar capillaries
• Between capillary beds in other tissues
© 2015 Pearson Education, Inc.
Figure 23-11 An Overview of the Key Steps in Respiration.
Respiration
External Respiration
Internal Respiration
Pulmonary
ventilation
O2 transport
Tissues
Gas
diffusion
Gas
diffusion
Gas
diffusion
Gas
diffusion
Lungs
CO2 transport
© 2015 Pearson Education, Inc.
23-6 Introduction to Gas Exchange
• Abnormal External Respiration Is Dangerous
• Hypoxia
• Low tissue oxygen levels
• Anoxia
• Complete lack of oxygen
© 2015 Pearson Education, Inc.
23-7 Pulmonary Ventilation
• Pulmonary Ventilation
• Is the physical movement of air in and out of
respiratory tract
• Provides alveolar ventilation
• The Movement of Air
• Atmospheric pressure
• The weight of air
• Has several important physiological effects
© 2015 Pearson Education, Inc.
23-7 Pulmonary Ventilation
• Gas Pressure and Volume
• Boyle’s Law
• Defines the relationship between gas pressure and
volume
P = 1/V
• In a contained gas:
• External pressure forces molecules closer together
• Movement of gas molecules exerts pressure on
container
© 2015 Pearson Education, Inc.
Figure 23-12 The Relationship between Gas Pressure and Volume.
a If you decrease the volume of the
container, collisions occur more
often per unit of time, increasing
the pressure of the gas.
b If you increase the volume,
fewer collisions occur per unit
of time, because it takes longer
for a gas molecule to travel from
one wall to another. As a result,
the gas pressure inside the
container decreases.
© 2015 Pearson Education, Inc.
Figure 23-12a The Relationship between Gas Pressure and Volume.
a If you decrease the volume of the
container, collisions occur more
often per unit of time, increasing
the pressure of the gas.
© 2015 Pearson Education, Inc.
Figure 23-12b The Relationship between Gas Pressure and Volume.
b If you increase the volume,
fewer collisions occur per unit
of time, because it takes longer
for a gas molecule to travel from
one wall to another. As a result,
the gas pressure inside the
container decreases.
© 2015 Pearson Education, Inc.
23-7 Pulmonary Ventilation
• Pressure and Airflow to the Lungs
• Air flows from area of higher pressure to area of
lower pressure
• A Respiratory Cycle
• Consists of:
• An inspiration (inhalation)
• An expiration (exhalation)
© 2015 Pearson Education, Inc.
23-7 Pulmonary Ventilation
• Pulmonary Ventilation
• Causes volume changes that create changes in
pressure
• Volume of thoracic cavity changes
• With expansion or contraction of diaphragm or rib
cage
© 2015 Pearson Education, Inc.
Figure 23-13a Mechanisms of Pulmonary Ventilation.
Ribs and
sternum
elevate
Diaphragm
contracts
a
© 2015 Pearson Education, Inc.
As the rib cage is elevated or
the diaphragm is depressed,
the volume of the thoracic
cavity increases.
Figure 23-13b Mechanisms of Pulmonary Ventilation.
Thoracic wall
Parietal pleura
Pleural fluid
Pleural
cavity
Lung
Cardiac
notch
Diaphragm
Poutside = Pinside
Pressure outside and inside are
equal, so no air movement occurs
b At rest, prior to inhalation.
© 2015 Pearson Education, Inc.
Visceral
pleura
Figure 23-13c Mechanisms of Pulmonary Ventilation.
Volume increases
Poutside > Pinside
Pressure inside decreases, so air flows in
c
Inhalation. Elevation of the rib cage and
contraction of the diaphragm increase the size
of the thoracic cavity. Pressure within the thoracic
cavity decreases, and air flows into the lungs.
© 2015 Pearson Education, Inc.
Figure 23-13d Mechanisms of Pulmonary Ventilation.
Volume decreases
Poutside < Pinside
Pressure inside increases, so air flows out
d
Exhalation. When the rib cage returns to its
original position and the diaphragm relaxes, the
volume of the thoracic cavity decreases. Pressure
increases, and air moves out of the lungs.
© 2015 Pearson Education, Inc.
23-7 Pulmonary Ventilation
• Compliance
•
•
•
•
An indicator of expandability
Low compliance requires greater force
High compliance requires less force
Factors That Affect Compliance
• Connective tissue structure of the lungs
• Level of surfactant production
• Mobility of the thoracic cage
© 2015 Pearson Education, Inc.
23-7 Pulmonary Ventilation
• Pressure Changes during Inhalation and
Exhalation
• Can be measured inside or outside the lungs
• Normal atmospheric pressure
• 1 atm = 760 mm Hg
© 2015 Pearson Education, Inc.
23-7 Pulmonary Ventilation
• The Intrapulmonary Pressure
• Also called intra-alveolar pressure
• Is relative to atmospheric pressure
• In relaxed breathing, the difference between
atmospheric pressure and intrapulmonary
pressure is small
• About 1 mm Hg on inhalation or 1 mm Hg on
exhalation
© 2015 Pearson Education, Inc.
23-7 Pulmonary Ventilation
• Maximum Intrapulmonary Pressure
• Maximum straining, a dangerous activity, can
increase range
• From 30 mm Hg to 100 mm Hg
© 2015 Pearson Education, Inc.
23-7 Pulmonary Ventilation
• The Intrapleural Pressure
• Pressure in space between parietal and visceral
pleura
• Averages 4 mm Hg
• Maximum of 18 mm Hg
• Remains below atmospheric pressure throughout
respiratory cycle
© 2015 Pearson Education, Inc.
Table 23-1 The Four Most Common Methods of Reporting Gas Pressures.
© 2015 Pearson Education, Inc.
23-7 Pulmonary Ventilation
• The Respiratory Cycle
• Cyclical changes in intrapleural pressure operate
the respiratory pump
• Which aids in venous return to heart
• Tidal Volume (VT)
• Amount of air moved in and out of lungs in a single
respiratory cycle
© 2015 Pearson Education, Inc.
23-7 Pulmonary Ventilation
• Injury to the Chest Wall
• Pneumothorax allows air into pleural cavity
• Atelectasis (also called a collapsed lung) is a
result of pneumothorax
© 2015 Pearson Education, Inc.
Figure 23-14 Pressure and Volume Changes during Inhalation and Exhalation.
INHALATION EXHALATION
Intrapulmonary
pressure
(mm Hg)
Trachea
+2
+1
a Changes in intrapulmonary
0
pressure during a single
respiratory cycle
−1
Bronchi
Intrapleural
pressure
(mm Hg)
Lung
−2
−3
b Changes in intrapleural
−4
Diaphragm
pressure during a single
respiratory cycle
−5
Right pleural
cavity
Left pleural
cavity
−6
Tidal
volume
(mL)
500
c A plot of tidal volume, the
250
amount of air moving into
and out of the lungs during a
single respiratory cycle
0
© 2015 Pearson Education, Inc.
1
2
3
Time (sec)
4
23-7 Pulmonary Ventilation
• The Respiratory Muscles
• Most important are:
• The diaphragm
• External intercostal muscles of the ribs
• Accessory respiratory muscles
• Activated when respiration increases significantly
© 2015 Pearson Education, Inc.
23-7 Pulmonary Ventilation
• The Mechanics of Breathing
• Inhalation
• Always active
• Exhalation
• Active or passive
© 2015 Pearson Education, Inc.
23-7 Pulmonary Ventilation
• Muscles Used in Inhalation
• Diaphragm
• Contraction draws air into lungs
• 75 percent of normal air movement
• External intercostal muscles
• Assist inhalation
• 25 percent of normal air movement
• Accessory muscles assist in elevating ribs
•
•
•
•
Sternocleidomastoid
Serratus anterior
Pectoralis minor
Scalene muscles
© 2015 Pearson Education, Inc.
Figure 23-15 Respiratory Muscles and Pulmonary Ventilation (Part 1 of 4).
The Respiratory Muscles
The most important skeletal muscles involved in respiratory movements are the
diaphragm and the external intercostals. These muscles are the primary
respiratory muscles and are active during normal breathing at rest. The
accessory respiratory muscles become active when the depth and frequency
of respiration must be increased markedly.
Accessory
Respiratory Muscles
Sternocleidomastoid
muscle
Scalene muscles
Pectoralis minor
muscle
Serratus anterior
muscle
Primary
Respiratory Muscles
Diaphragm
Primary
Respiratory Muscles
External intercostal
muscles
Accessory
Respiratory Muscles
Internal intercostal
muscles
Transversus thoracis
muscle
External oblique
muscle
Rectus abdominis
Internal oblique
muscle
© 2015 Pearson Education, Inc.
Figure 23-15 Respiratory Muscles and Pulmonary Ventilation (Part 2 of 4).
The Mechanics of Breathing
Pulmonary ventilation, air movement into
and out of the respiratory system, occurs by
changing the volume of the lungs. The
changes in volume take place through the
contraction of skeletal
muscles. As the ribs
are elevated or
Ribs and
the diaphragm is
sternum
elevate
depressed, the
volume of the
thoracic cavity
increases and air
moves into the
lungs. The outward
Diaphragm
movement of the
contracts
ribs as they are
elevated resembles
the outward swing
KEY
of a raised bucket
= Movement of rib cage
handle.
= Movement of diaphragm
= Muscle contraction
© 2015 Pearson Education, Inc.
Figure 23-15 Respiratory Muscles and Pulmonary Ventilation (Part 3 of 4).
Respiratory Movements
Respiratory muscles may be used in various combinations, depending on the
volume of air that must be moved in or out of the lungs. In quiet breathing,
inhalation involves muscular contractions, but exhalation is a passive process.
Forced breathing calls upon the accessory muscles to assist with inhalation,
and exhalation involves contraction by the transversus thoracis, internal
intercostal, and rectus abdominis muscles.
Inhalation
Inhalation is an
active process.
It primarily
involves the
diaphragm
and the
external
intercostal
muscles,
with
assistance
from the
accessory
respiratory
muscles as
needed.
Accessory Respiratory
Muscles (Inhalation)
Sternocleidomastoid
muscle
Scalene muscles
Pectoralis minor muscle
Serratus anterior muscle
Primary Respiratory
Muscles (Inhalation)
External intercostal
muscles
Diaphragm
KEY
= Movement of rib cage
= Movement of diaphragm
= Muscle contraction
© 2015 Pearson Education, Inc.
23-7 Pulmonary Ventilation
• Muscles Used in Exhalation
• Internal intercostal and transversus thoracis
muscles
• Depress the ribs
• Abdominal muscles
• Compress the abdomen
• Force diaphragm upward
© 2015 Pearson Education, Inc.
Figure 23-15 Respiratory Muscles and Pulmonary Ventilation (Part 4 of 4).
Respiratory Movements
Respiratory muscles may be used in various combinations, depending on the
volume of air that must be moved in or out of the lungs. In quiet breathing,
inhalation involves muscular contractions, but exhalation is a passive process.
Forced breathing calls upon the accessory muscles to assist with inhalation,
and exhalation involves contraction by the transversus thoracis, internal
intercostal, and rectus abdominis muscles.
Exhalation
During forced
exhalation, the
transversus thoracis
and internal
intercostal muscles
actively depress
the ribs, and
the abdominal
muscles
(external and
internal obliques,
transversus
abdominis, and
rectus abdominis)
compress the
abdomen and push
the diaphragm up.
Accessory
Respiratory
Muscles
(Exhalation)
Transversus
thoracis
muscle
Internal
intercostal
muscles
Rectus
abdominis
KEY
= Movement of rib cage
= Movement of diaphragm
= Muscle contraction
© 2015 Pearson Education, Inc.
23-7 Pulmonary Ventilation
• Modes of Breathing
• Respiratory movements are classified
• By pattern of muscle activity
• Quiet breathing
• Forced breathing
© 2015 Pearson Education, Inc.
23-7 Pulmonary Ventilation
• Quiet Breathing (Eupnea)
• Involves active inhalation and passive exhalation
• Diaphragmatic breathing or deep breathing
• Is dominated by diaphragm
• Costal breathing or shallow breathing
• Is dominated by rib cage movements
© 2015 Pearson Education, Inc.
23-7 Pulmonary Ventilation
• Elastic Rebound
• When inhalation muscles relax
• Elastic components of muscles and lungs recoil
• Returning lungs and alveoli to original position
© 2015 Pearson Education, Inc.
23-7 Pulmonary Ventilation
• Forced Breathing (Hyperpnea)
• Involves active inhalation and exhalation
• Assisted by accessory muscles
• Maximum levels occur in exhaustion
© 2015 Pearson Education, Inc.
23-7 Pulmonary Ventilation
• Respiratory Rates and Volumes
• Respiratory system adapts to changing oxygen
demands by varying:
• The number of breaths per minute (respiratory
rate)
• The volume of air moved per breath (tidal volume)
© 2015 Pearson Education, Inc.
23-7 Pulmonary Ventilation
• The Respiratory Minute Volume (VE)
• Amount of air moved per minute
• Is calculated by:
respiratory rate  tidal volume
• Measures pulmonary ventilation
© 2015 Pearson Education, Inc.
23-7 Pulmonary Ventilation
• Alveolar Ventilation (VA)
• Only a part of respiratory minute volume reaches
alveolar exchange surfaces
• Volume of air remaining in conducting passages is
anatomic dead space
• Alveolar ventilation is the amount of air reaching
alveoli each minute
• Calculated as:
(tidal volume  anatomic dead space)  respiratory rate
© 2015 Pearson Education, Inc.
23-7 Pulmonary Ventilation
• Alveolar Gas Content
• Alveoli contain less O2, more CO2 than
atmospheric air
• Because air mixes with exhaled air
© 2015 Pearson Education, Inc.
23-7 Pulmonary Ventilation
• Relationships among VT, VE, and VA
• Determined by respiratory rate and tidal volume
• For a given respiratory rate:
• Increasing tidal volume increases alveolar
ventilation rate
• For a given tidal volume:
• Increasing respiratory rate increases alveolar
ventilation
© 2015 Pearson Education, Inc.
23-7 Pulmonary Ventilation
• Respiratory Performance and Volume
Relationships
• Total lung volume is divided into a series of
volumes and capacities useful in diagnosing
problems
• Four Pulmonary Volumes
1.
2.
3.
4.
© 2015 Pearson Education, Inc.
Resting tidal volume (Vt)
Expiratory reserve volume (ERV)
Residual volume
Inspiratory reserve volume (IRV)
23-7 Pulmonary Ventilation
• Resting Tidal Volume (Vt)
• In a normal respiratory cycle
• Expiratory Reserve Volume (ERV)
• After a normal exhalation
• Residual Volume
• After maximal exhalation
• Minimal volume (in a collapsed lung)
• Inspiratory Reserve Volume (IRV)
• After a normal inspiration
© 2015 Pearson Education, Inc.
23-7 Pulmonary Ventilation
• Four Calculated Respiratory Capacities
1. Inspiratory capacity
• Tidal volume + inspiratory reserve volume
2. Functional residual capacity (FRC)
• Expiratory reserve volume + residual volume
3. Vital capacity
• Expiratory reserve volume + tidal volume +
inspiratory reserve volume
© 2015 Pearson Education, Inc.
23-7 Pulmonary Ventilation
• Four Calculated Respiratory Capacities
4. Total lung capacity
• Vital capacity + residual volume
• Pulmonary Function Tests
• Measure rates and volumes of air movements
© 2015 Pearson Education, Inc.
Figure 23-16 Pulmonary Volumes and Capacities.
Pulmonary Volumes and Capacities (adult male)
6000
Sex Differences
Tidal volume
(VT = 500 mL)
Inspiratory
capacity
Inspiratory
reserve
volume (IRV)
Volume (mL)
Total lung
capacity
Expiratory
reserve
volume (ERV)
Functional
residual
capacity
(FRC)
1200
0
Residual
volume
Time
© 2015 Pearson Education, Inc.
1900
500
500
ERV 1000
700
Residual volume 1200
1100
VT
Total lung capacity 6000 mL
2200
Minimal volume
(30–120 mL)
IRV 3300
Vital
capacity
Vital
capacity
2700
Females
Males
4200 mL
Inspiratory
capacity
Functional
residual
capacity
23-8 Gas Exchange
• Gas Exchange
• Occurs between blood and alveolar air
• Across the respiratory membrane
• Depends on:
1. Partial pressures of the gases
2. Diffusion of molecules between gas and liquid
© 2015 Pearson Education, Inc.
23-8 Gas Exchange
• The Gas Laws
• Diffusion occurs in response to concentration
gradients
• Rate of diffusion depends on physical principles,
or gas laws
• For example, Boyle’s law
© 2015 Pearson Education, Inc.
23-8 Gas Exchange
• Dalton’s Law and Partial Pressures
• Composition of Air
•
•
•
•
Nitrogen (N2) is about 78.6 percent
Oxygen (O2) is about 20.9 percent
Water vapor (H2O) is about 0.5 percent
Carbon dioxide (CO2) is about 0.04 percent
© 2015 Pearson Education, Inc.
23-8 Gas Exchange
• Dalton’s Law and Partial Pressures
• Atmospheric pressure (760 mm Hg)
• Produced by air molecules bumping into each other
• Each gas contributes to the total pressure
• In proportion to its number of molecules (Dalton’s
law)
© 2015 Pearson Education, Inc.
23-8 Gas Exchange
• Partial Pressure
• The pressure contributed by each gas in the
atmosphere
• All partial pressures together add up to 760 mm
Hg
© 2015 Pearson Education, Inc.
23-8 Gas Exchange
• Diffusion between Liquids and Gases
• Henry’s Law
• When gas under pressure comes in contact with
liquid:
• Gas dissolves in liquid until equilibrium is reached
• At a given temperature:
• Amount of a gas in solution is proportional to partial
pressure of that gas
• The actual amount of a gas in solution (at given
partial pressure and temperature):
• Depends on the solubility of that gas in that
particular liquid
© 2015 Pearson Education, Inc.
Figure 23-17 Henry’s Law and the Relationship between Solubility and Pressure.
Example
Soda is put into
the can under
pressure, and the
gas (carbon
dioxide) is in
solution at
equilibrium.
a Increasing the pressure drives gas molecules into
solution until an equilibrium is established.
Example
Opening the can of
soda relieves the
pressure, and
bubbles form as
the dissolved gas
leaves the solution.
b When the gas pressure decreases, dissolved
gas molecules leave the solution until a new
equilibrium is reached.
© 2015 Pearson Education, Inc.
Figure 23-17a Henry’s Law and the Relationship between Solubility and Pressure.
Example
Soda is put into
the can under
pressure, and the
gas (carbon
dioxide) is in
solution at
equilibrium.
a Increasing the pressure drives gas molecules into
solution until an equilibrium is established.
© 2015 Pearson Education, Inc.
Figure 23-17b Henry’s Law and the Relationship between Solubility and Pressure.
Example
Opening the can of
soda relieves the
pressure, and
bubbles form as
the dissolved gas
leaves the solution.
b When the gas pressure decreases, dissolved
gas molecules leave the solution until a new
equilibrium is reached.
© 2015 Pearson Education, Inc.
23-8 Gas Exchange
• Solubility in Body Fluids
• CO2 is very soluble
• O2 is less soluble
• N2 has very low solubility
© 2015 Pearson Education, Inc.
23-8 Gas Exchange
• Normal Partial Pressures
• In pulmonary vein plasma
• PCO = 40 mm Hg
2
• PO = 100 mm Hg
2
• PN = 573 mm Hg
2
© 2015 Pearson Education, Inc.
Table 23-1 The Four Most Common Methods of Reporting Gas Pressures.
© 2015 Pearson Education, Inc.
23-8 Gas Exchange
• Diffusion and Respiratory Function
• Direction and rate of diffusion of gases across the
respiratory membrane
• Determine different partial pressures and
solubilities
© 2015 Pearson Education, Inc.
23-8 Gas Exchange
• Five Reasons for Efficiency of Gas Exchange
1. Substantial differences in partial pressure across
the respiratory membrane
2. Distances involved in gas exchange are short
3. O2 and CO2 are lipid soluble
4. Total surface area is large
5. Blood flow and airflow are coordinated
© 2015 Pearson Education, Inc.
23-8 Gas Exchange
• Partial Pressures in Alveolar Air and Alveolar
Capillaries
• Blood arriving in pulmonary arteries has:
• Low PO
2
• High PCO
2
• The concentration gradient causes:
• O2 to enter blood
• CO2 to leave blood
• Rapid exchange allows blood and alveolar air to
reach equilibrium
© 2015 Pearson Education, Inc.
23-8 Gas Exchange
• Partial Pressures in the Systemic Circuit
• Oxygenated blood mixes with deoxygenated blood
from conducting passageways
• Lowers the PO2 of blood entering systemic circuit
(drops to about 95 mm Hg)
© 2015 Pearson Education, Inc.
23-8 Gas Exchange
• Partial Pressures in the Systemic Circuit
• Interstitial Fluid
• PO 40 mm Hg
2
• PCO 45 mm Hg
2
• Concentration gradient in peripheral capillaries is
opposite of lungs
• CO2 diffuses into blood
• O2 diffuses out of blood
© 2015 Pearson Education, Inc.
Figure 23-18a An Overview of Respiratory Processes and Partial Pressures in Respiration.
a External Respiration
PO = 40
2
PCO2 = 45
Alveolus
Respiratory
membrane
Systemic
circuit
Pulmonary
circuit
PO = 100
2
PCO2 = 40
Pulmonary
capillary
Systemic
circuit
© 2015 Pearson Education, Inc.
PO = 100
2
PCO2 = 40
Figure 23-18b An Overview of Respiratory Processes and Partial Pressures in Respiration.
Systemic
circuit
Pulmonary
circuit
b Internal Respiration
Interstitial fluid
Systemic
circuit
PO2 = 95
PCO2 = 40
PO2 = 40
PCO2 = 45
PO2 = 40
PCO2 = 45
© 2015 Pearson Education, Inc.
Systemic
capillary
23-9 Gas Transport
• Gas Pickup and Delivery
• Blood plasma cannot transport enough O2 or CO2
to meet physiological needs
• Red Blood Cells (RBCs)
• Transport O2 to, and CO2 from, peripheral tissues
• Remove O2 and CO2 from plasma, allowing gases
to diffuse into blood
© 2015 Pearson Education, Inc.
23-9 Gas Transport
• Oxygen Transport
• O2 binds to iron ions in hemoglobin (Hb)
molecules
• In a reversible reaction
• New molecule is called oxyhemoglobin (HbO2)
• Each RBC has about 280 million Hb molecules
• Each binds four oxygen molecules
© 2015 Pearson Education, Inc.
23-9 Gas Transport
• Hemoglobin Saturation
• The percentage of heme units in a hemoglobin
molecule that contain bound oxygen
• Environmental Factors Affecting Hemoglobin
•
•
•
•
PO of blood
2
Blood pH
Temperature
Metabolic activity within RBCs
© 2015 Pearson Education, Inc.
23-9 Gas Transport
• Oxygen–Hemoglobin Saturation Curve
• A graph relating the saturation of hemoglobin to
partial pressure of oxygen
• Higher PO results in greater Hb saturation
2
• Curve rather than a straight line because Hb
changes shape each time a molecule of O2 is
bound
• Each O2 bound makes next O2 binding easier
• Allows Hb to bind O2 when O2 levels are low
© 2015 Pearson Education, Inc.
23-9 Gas Transport
• Oxygen Reserves
• O2 diffuses
• From peripheral capillaries (high PO )
2
• Into interstitial fluid (low PO )
2
• Amount of O2 released depends on interstitial PO
2
• Up to 3/4 may be reserved by RBCs
© 2015 Pearson Education, Inc.
23-9 Gas Transport
• Carbon Monoxide
• CO from burning fuels
• Binds strongly to hemoglobin
• Takes the place of O2
• Can result in carbon monoxide poisoning
© 2015 Pearson Education, Inc.
23-9 Gas Transport
• The Oxygen–Hemoglobin Saturation Curve
• Is standardized for normal blood (pH 7.4, 37C)
• When pH drops or temperature rises:
• More oxygen is released
• Curve shifts to right
• When pH rises or temperature drops:
• Less oxygen is released
• Curve shifts to left
© 2015 Pearson Education, Inc.
Figure 23-19 An Oxygen–Hemoglobin Saturation Curve.
100
Oxyhemoglobin (% saturation)
90
80
70
% saturation
P O2
of Hb
(mm Hg)
10
13.5
20
35
30
57
40
75
50
83.5
60
89
70
92.7
80
94.5
90
96.5
100
97.5
60
50
40
30
20
10
0
© 2015 Pearson Education, Inc.
20
40
60
P O2 (mm Hg)
80
100
23-9 Gas Transport
• Hemoglobin and pH
• Bohr effect is the result of pH on hemoglobinsaturation curve
• Caused by CO2
• CO2 diffuses into RBC
• An enzyme, called carbonic anhydrase, catalyzes
reaction with H2O
• Produces carbonic acid (H2CO3)
• Dissociates into hydrogen ion (H+) and bicarbonate
ion (HCO3)
• Hydrogen ions diffuse out of RBC, lowering pH
© 2015 Pearson Education, Inc.
Figure 23-20a The Effects of pH and Temperature on Hemoglobin Saturation.
100
Oxyhemoglobin (% saturation)
80
7.6
7.4
7.2
60
40
Normal blood pH range
7.35–7.45
20
0
20
40
60
P O2 (mm Hg)
80
100
a Effect of pH. When the pH decreases below normal
levels, more oxygen is released; the oxygen–hemoglobin
saturation curve shifts to the right. When the pH increases,
less oxygen is released; the curve shifts to the left.
© 2015 Pearson Education, Inc.
23-9 Gas Transport
• Hemoglobin and Temperature
• Temperature increase = hemoglobin releases
more oxygen
• Temperature decrease = hemoglobin holds
oxygen more tightly
• Temperature effects are significant only in active
tissues that are generating large amounts of heat
• For example, active skeletal muscles
© 2015 Pearson Education, Inc.
Figure 23-20b The Effects of pH and Temperature on Hemoglobin Saturation.
100
20C
10C
38C
Oxyhemoglobin (% saturation)
43C
80
60
40
Normal blood temperature
38C
20
0
20
40
60
80
100
P O2 (mm Hg)
b Effect of temperature. When the temperature
increases, more oxygen is released; the
oxygen–hemoglobin saturation curve shifts to the
right.
© 2015 Pearson Education, Inc.
23-9 Gas Transport
• Hemoglobin and BPG
• 2,3-bisphosphoglycerate (BPG)
• RBCs generate ATP by glycolysis
• Forming lactic acid and BPG
• BPG directly affects O2 binding and release
• More BPG, more oxygen released
© 2015 Pearson Education, Inc.
23-9 Gas Transport
• BPG Levels
• BPG levels rise:
• When pH increases
• When stimulated by certain hormones
• If BPG levels are too low:
• Hemoglobin will not release oxygen
© 2015 Pearson Education, Inc.
23-9 Gas Transport
• Fetal Hemoglobin
• The structure of fetal hemoglobin
• Differs from that of adult Hb
• At the same PO :
2
• Fetal Hb binds more O2 than adult Hb
• Which allows fetus to take O2 from maternal blood
© 2015 Pearson Education, Inc.
Figure 23-21 A Functional Comparison of Fetal and Adult Hemoglobin.
Oxyhemoglobin (% saturation)
100
90
80
70
Fetal hemoglobin
60
Adult hemoglobin
50
40
30
20
10
0
© 2015 Pearson Education, Inc.
20
40
60
80
PO2 (mm Hg)
100
120
23-9 Gas Transport
• Carbon Dioxide Transport (CO2)
• Is generated as a by-product of aerobic
metabolism (cellular respiration)
• CO2 in the bloodstream can be carried three ways
1. Converted to carbonic acid
2. Bound to hemoglobin within red blood cells
3. Dissolved in plasma
© 2015 Pearson Education, Inc.
23-9 Gas Transport
• Carbonic Acid Formation
• 70 percent is transported as carbonic acid
(H2CO3)
• Which dissociates into H+ and bicarbonate (HCO3)
• Hydrogen ions bind to hemoglobin
• Bicarbonate Ions
• Move into plasma by an exchange mechanism
(the chloride shift) that takes in Cl ions without
using ATP
© 2015 Pearson Education, Inc.
23-9 Gas Transport
• CO2 Binding to Hemoglobin
• 23 percent is bound to amino groups of globular
proteins in Hb molecule
• Forming carbaminohemoglobin
• Transport in Plasma
• 7 percent is transported as CO2 dissolved in
plasma
© 2015 Pearson Education, Inc.
Figure 23-22 Carbon Dioxide Transport in Blood.
CO2 diffuses
into the
bloodstream
7% remains
dissolved in
plasma (as CO2)
93% diffuses
into RBCs
23% binds to Hb,
forming
carbaminohemoglobin,
Hb•CO2
RBC
H+ removed
by buffers,
especially Hb
PLASMA
© 2015 Pearson Education, Inc.
70% converted to
H2CO3 by carbonic
anhydrase
H2CO3 dissociates
into H+ and HCO3−
H+
Cl−
HCO3− moves
out of RBC in
exchange for
Cl− (chloride
shift)
Figure 23-23 A Summary of the Primary Gas Transport Mechanisms.
O2 delivery
O2 pickup
Pulmonary
capillary
Plasma
Systemic
capillary
Red blood cell
Red blood cell
Hb
Hb
Hb
O2
O2
O2
Alveolar
air space
O2
O2
O2
O2
Hb
Cells in
peripheral
tissues
O2
HCO3−
Cl−
Alveolar
air space
HCO3−
Hb
Hb
H+ + HCO3−
Hb
H+
H2CO3
H2CO3
CO2
CO2
CO2
Hb
H2O
CO2 delivery
CO2
H2O
Hb
CO2
Hb
Pulmonary
capillary
© 2015 Pearson Education, Inc.
H+
Hb
Hb
Cl−
H+ + HCO3−
Chloride
shift
CO2
CO2
Cells in
peripheral
tissues
Systemic
capillary
CO2 pickup
Figure 23-23 A Summary of the Primary Gas Transport Mechanisms (Part 1 of 4).
O2 pickup
Pulmonary
capillary
Plasma
Red blood cell
Hb
Hb
O2
O2
Alveolar
air space
© 2015 Pearson Education, Inc.
O2
O2
Figure 23-23 A Summary of the Primary Gas Transport Mechanisms (Part 2 of 4).
O2 delivery
Systemic
capillary
Red blood cell
Hb
O2
O2
O2
Hb
O2
Cells in
peripheral
tissues
© 2015 Pearson Education, Inc.
Figure 23-23 A Summary of the Primary Gas Transport Mechanisms (Part 3 of 4).
Cl−
Alveolar
air space
HCO3−
Hb
H+ + HCO3−
Hb
H+
H2CO3
CO2
CO2
CO2
H2O
Hb
Hb
CO2
Pulmonary
capillary
CO2 delivery
© 2015 Pearson Education, Inc.
Figure 23-23 A Summary of the Primary Gas Transport Mechanisms (Part 4 of 4).
HCO3−
Cl−
H+ + HCO3−
Chloride
shift
Hb
H2CO3
Hb H+
CO2
H2O
Hb
Hb
CO2
Cells in
peripheral
tissues
Systemic
capillary
CO2 pickup
© 2015 Pearson Education, Inc.
CO2
23-10 Control of Respiration
• Peripheral and Alveolar Capillaries
• Maintain balance during gas diffusion by:
1. Changes in blood flow and oxygen delivery
2. Changes in depth and rate of respiration
© 2015 Pearson Education, Inc.
23-10 Control of Respiration
• Local Regulation of Gas Transport and Alveolar
Function
• Rising PCO2 levels
• Relax smooth muscle in arterioles and capillaries
• Increase blood flow
• Coordination of lung perfusion and alveolar
ventilation
• Shifting blood flow
• PCO2 levels
• Control bronchoconstriction and bronchodilation
© 2015 Pearson Education, Inc.
23-10 Control of Respiration
• The Respiratory Centers of the Brain
• When oxygen demand rises:
• Cardiac output and respiratory rates increase
under neural control
• Have both voluntary and involuntary components
© 2015 Pearson Education, Inc.
23-10 Control of Respiration
• The Respiratory Centers of the Brain
• Voluntary centers in cerebral cortex affect:
• Respiratory centers of pons and medulla oblongata
• Motor neurons that control respiratory muscles
• The Respiratory Centers
• Three pairs of nuclei in the reticular formation of
medulla oblongata and pons
• Regulate respiratory muscles
• In response to sensory information via respiratory
reflexes
© 2015 Pearson Education, Inc.
23-10 Control of Respiration
• Respiratory Centers of the Medulla Oblongata
• Set the pace of respiration
• Can be divided into two groups
1. Dorsal respiratory group (DRG)
2. Ventral respiratory group (VRG)
© 2015 Pearson Education, Inc.
23-10 Control of Respiration
• Dorsal Respiratory Group (DRG)
• Inspiratory center
• Functions in quiet and forced breathing
• Ventral Respiratory Group (VRG)
• Inspiratory and expiratory center
• Functions only in forced breathing
© 2015 Pearson Education, Inc.
23-10 Control of Respiration
• Quiet Breathing
• Brief activity in the DRG
• Stimulates inspiratory muscles
• DRG neurons become inactive
• Allowing passive exhalation
© 2015 Pearson Education, Inc.
Figure 23-24a Basic Regulatory Patterns of Respiration.
a Quiet Breathing
INHALATION
(2 seconds)
Diaphragm and external
intercostal muscles
contract and inhalation
occurs.
Dorsal
respiratory
group active
Dorsal
respiratory
group inhibited
Diaphragm and external
intercostal muscles
relax and passive
exhalation occurs.
EXHALATION
(3 seconds)
© 2015 Pearson Education, Inc.
23-10 Control of Respiration
• Forced Breathing
• Increased activity in DRG
• Stimulates VRG
• Which activates accessory inspiratory muscles
• After inhalation
• Expiratory center neurons stimulate active
exhalation
© 2015 Pearson Education, Inc.
Figure 23-24b Basic Regulatory Patterns of Respiration.
b Forced Breathing
INHALATION
Muscles of inhalation
contract, and opposing
muscles relax.
Inhalation occurs.
DRG and
inspiratory
center of VRG
are inhibited.
Expiratory
center of VRG
is active.
DRG and
inspiratory center
of VRG are active.
Expiratory center
of VRG is
inhibited.
Muscles of inhalation
relax and muscles of
exhalation contract.
Exhalation occurs.
EXHALATION
© 2015 Pearson Education, Inc.
23-10 Control of Respiration
• The Apneustic and Pneumotaxic Centers of the
Pons
• Paired nuclei that adjust output of respiratory
rhythmicity centers
• Regulating respiratory rate and depth of respiration
• Apneustic Center
• Provides continuous stimulation to its DRG center
• Pneumotaxic Centers
• Inhibit the apneustic centers
• Promote passive or active exhalation
© 2015 Pearson Education, Inc.
23-10 Control of Respiration
• Respiratory Centers and Reflex Controls
• Interactions between VRG and DRG
• Establish basic pace and depth of respiration
• The pneumotaxic center
• Modifies the pace
© 2015 Pearson Education, Inc.
LEVEL 3
Higher Centers
LEVEL 2
Figure 23-25 Control of Respiration (Part 3 of 6).
Apneustic and
Pneumotaxic Centers
Higher centers in the hypothalamus, limbic
system, and cerebral cortex can alter the
activity of the pneumotaxic centers, but
essentially normal respiratory cycles
continue even if the brain stem superior to
the pons has been severely damaged.
The apneustic (ap-NŪ-stik) centers
and the pneumotaxic
(nū-mō-TAKS-ik) centers of the
pons are paired nuclei that adjust
the output of the respiratory
rhythmicity centers.
Higher Centers
• Cerebral cortex
• Limbic system
• Hypothalamus
The pneumotaxic centers inhibit the apneustic centers and
promote passive or active exhalation. An increase in
pneumotaxic output quickens the pace of respiration by
shortening the duration of each inhalation. A decrease in
pneumotaxic output slows the respiratory pace but increases
the depth of respiration, because the apneustic centers are
more active.
The apneustic centers promote inhalation by stimulating the
DRG. During forced breathing, the apneustic centers adjust
the degree of stimulation in response to sensory information
from N X (the vagus nerve) concerning the amount of lung
inflation.
Medulla
oblongata
© 2015 Pearson Education, Inc.
Pons
Figure 23-25 Control of Respiration (Part 4 of 6).
LEVEL 1
Pons
© 2015 Pearson Education, Inc.
Respiratory
Rhythmicity Centers
The most basic level of respiratory control To diaphragm
involves pacemaker cells in the medulla
oblongata. These neurons generate cycles
of contraction and relaxation in the
diaphragm. The respiratory rhythmicity
To external
intercostal
centers set the pace of respiration by
muscles
adjusting the activities of these pacemakers and coordinating the activities
of additional respiratory muscles. Each
rhythmicity center can be subdivided into
a dorsal respiratory group (DRG) and a
ventral respiratory group (VRG). The
DRG is mainly concerned with inspiration To accessory
and the VRG is primarily associated with
inspiratory
expiration. The DRG modifies its activities
muscles
in response to input from chemoreceptors
and baroreceptors that monitor O 2, CO 2 ,
To accessory
and pH in the blood and CSF and from
expiratory
stretch receptors that monitor the degree
muscles
of stretching in the walls of the lungs.
Medulla
oblongata
The inspiratory center of
the DRG contains
neurons that control
lower motor neurons
innervating the external
intercostal muscles and
the diaphragm. This
center functions in
every respiratory cycle.
The VRG has inspiratory
and expiratory centers
that function only when
breathing demands
increase and accessory
muscles become
involved.
In addition to the centers in
the pons, the DRG, and the
VRG, the pre-Bötzinger
complex in the medulla is
essential to all forms of
breathing. Its mechanisms
are poorly understood.
23-10 Control of Respiration
• Sudden Infant Death Syndrome (SIDS)
• Disrupts normal respiratory reflex pattern
• May result from connection problems between
pacemaker complex and respiratory centers
© 2015 Pearson Education, Inc.
23-10 Control of Respiration
• Respiratory Reflexes
• Chemoreceptors are sensitive to PCO2, PO2, or pH
of blood or cerebrospinal fluid
• Baroreceptors in aortic or carotid sinuses are
sensitive to changes in blood pressure
• Stretch receptors respond to changes in lung
volume
• Irritating physical or chemical stimuli in nasal
cavity, larynx, or bronchial tree
• Other sensations including pain, changes in body
temperature, abnormal visceral sensations
© 2015 Pearson Education, Inc.
23-10 Control of Respiration
• The Chemoreceptor Reflexes
• Respiratory centers are strongly influenced by
chemoreceptor input from:
• Glossopharyngeal nerve (N IX)
• Vagus nerve (N X)
• Central chemoreceptors that monitor cerebrospinal
fluid
© 2015 Pearson Education, Inc.
23-10 Control of Respiration
• The Chemoreceptor Reflexes
• The glossopharyngeal nerve
• From carotid bodies
• Stimulated by changes in blood pH or PO
• The vagus nerve
2
• From aortic bodies
• Stimulated by changes in blood pH or PO
2
© 2015 Pearson Education, Inc.
23-10 Control of Respiration
• The Chemoreceptor Reflexes
• Central chemoreceptors that monitor
cerebrospinal fluid
• Are on ventrolateral surface of medulla oblongata
• Respond to PCO and pH of CSF
2
© 2015 Pearson Education, Inc.
23-10 Control of Respiration
• Chemoreceptor Stimulation
• Leads to increased depth and rate of respiration
• Is subject to adaptation
• Decreased sensitivity due to chronic stimulation
© 2015 Pearson Education, Inc.
23-10 Control of Respiration
• Hypercapnia
• An increase in arterial PCO
2
• Stimulates chemoreceptors in the medulla
oblongata
• To restore homeostasis
© 2015 Pearson Education, Inc.
23-10 Control of Respiration
• Hypercapnia and Hypocapnia
• Hypoventilation is a common cause of
hypercapnia
• Abnormally low respiration rate
• Allows CO2 buildup in blood
• Excessive ventilation, hyperventilation, results in
abnormally low PCO (hypocapnia)
2
• Stimulates chemoreceptors to decrease respiratory
rate
© 2015 Pearson Education, Inc.
Figure 23-26a The Chemoreceptor Response to Changes in PCO2.
Increased
arterial PCO2
a
An increase in arterial PCO2
stimulates chemoreceptors
that accelerate breathing
cycles at the inspiratory center.
This change increases the
respiratory rate, encourages
CO2 loss at the lungs, and
decreases arterial PCO2.
Stimulation
of arterial
chemoreceptors
Stimulation of
respiratory muscles
Increased PCO2,
decreased pH
in CSF
Stimulation of CSF
chemoreceptors at
medulla oblongata
Increased respiratory
rate with increased
elimination of CO2 at
alveoli
HOMEOSTASIS
DISTURBED
Increased
arterial PCO2
(hypercapnia)
HOMEOSTASIS
RESTORED
HOMEOSTASIS
Normal
arterial PCO2
© 2015 Pearson Education, Inc.
Start
Normal
arterial PCO2
Figure 23-26b The Chemoreceptor Response to Changes in PCO2.
HOMEOSTASIS
RESTORED
HOMEOSTASIS
Normal
arterial PCO2
b
A decrease in arterial PCO2
inhibits these chemoreceptors.
Without stimulation, the rate of
respiration decreases, slowing
the rate of CO2 loss at the
lungs, and increasing arterial
PCO2.
Decreased
arterial PCO2
Normal
arterial PCO2
HOMEOSTASIS
DISTURBED
Decreased respiratory
rate with decreased
elimination of CO2 at
alveoli
Decreased
arterial PCO2
(hypocapnia)
Decreased PCO2,
increased pH
in CSF
Inhibition of arterial
chemoreceptors
© 2015 Pearson Education, Inc.
Start
Decreased stimulation
of CSF chemoreceptors
Inhibition of
respiratory muscles
23-10 Control of Respiration
• The Baroreceptor Reflexes
• Carotid and aortic baroreceptor stimulation
• Affects blood pressure and respiratory centers
• When blood pressure falls:
• Respiration increases
• When blood pressure increases:
• Respiration decreases
© 2015 Pearson Education, Inc.
23-10 Control of Respiration
• The HeringBreuer Reflexes
• Two baroreceptor reflexes involved in forced
breathing
1. Inflation reflex
• Prevents overexpansion of lungs
2. Deflation reflex
• Inhibits expiratory centers
• Stimulates inspiratory centers during lung deflation
© 2015 Pearson Education, Inc.
23-10 Control of Respiration
• Protective Reflexes
• Triggered by receptors in epithelium of respiratory
tract when lungs are exposed to:
• Toxic vapors
• Chemical irritants
• Mechanical stimulation
• Cause sneezing, coughing, and laryngeal spasm
© 2015 Pearson Education, Inc.
23-10 Control of Respiration
• Apnea
• A period of suspended respiration
• Normally followed by explosive exhalation to clear
airways
• Sneezing and coughing
• Laryngeal Spasm
• Temporarily closes airway
• To prevent foreign substances from entering
© 2015 Pearson Education, Inc.
23-10 Control of Respiration
• Voluntary Control of Respiration
• Strong emotions can stimulate respiratory centers
in hypothalamus
• Emotional stress can activate sympathetic or
parasympathetic division of ANS
• Causing bronchodilation or bronchoconstriction
• Anticipation of strenuous exercise can increase
respiratory rate and cardiac output by sympathetic
stimulation
© 2015 Pearson Education, Inc.
23-10 Control of Respiration
• Changes in the Respiratory System at Birth
• Before birth
• Pulmonary vessels are collapsed
• Lungs contain no air
• During delivery
• Placental connection is lost
• Blood PO2 falls
• PCO2 rises
© 2015 Pearson Education, Inc.
23-10 Control of Respiration
• Changes in the Respiratory System at Birth
• At birth
• Newborn overcomes force of surface tension to
inflate bronchial tree and alveoli and take first
breath
• Large drop in pressure at first breath
• Pulls blood into pulmonary circulation
• Closing foramen ovale and ductus arteriosus
• Redirecting fetal blood circulation patterns
• Subsequent breaths fully inflate alveoli
© 2015 Pearson Education, Inc.
23-11 Effects of Aging on the Respiratory
System
• Three Effects of Aging on the Respiratory System
1. Elastic tissues deteriorate
• Altering lung compliance and lowering vital
capacity
2. Arthritic changes
• Restrict chest movements
• Limit respiratory minute volume
3. Emphysema
• Affects individuals over age 50
• Depending on exposure to respiratory irritants
(e.g., cigarette smoke)
© 2015 Pearson Education, Inc.
Figure 23-27 Decline in Respiratory Performance with Age and Smoking.
100
Respiratory performance
(% of value at age 25)
Never smoked
75
Regular
smoker
Stopped
at age 45
50
Disability
Stopped
at age 65
25
Death
0
25
© 2015 Pearson Education, Inc.
50
Age (years)
75
23-12 Respiratory System Integration
• Respiratory Activity
• Maintaining homeostatic O2 and CO2 levels in
peripheral tissues requires coordination between
several systems
• Particularly the respiratory and cardiovascular
systems
© 2015 Pearson Education, Inc.
23-12 Respiratory System Integration
• Coordination of Respiratory and Cardiovascular
Systems
• Improves efficiency of gas exchange by controlling
lung perfusion
• Increases respiratory drive through chemoreceptor
stimulation
• Raises cardiac output and blood flow through
baroreceptor stimulation
© 2015 Pearson Education, Inc.
Figure 23-28 diagrams the functional relationships between the respiratory system and the other body systems we have studied so far.
© 2015 Pearson Education, Inc.