169 Ch 23_lecture_presentation

© 2012 Pearson Education, Inc.
PowerPoint®
Lecture Presentations prepared by
Jason LaPres
Lone Star College—North Harris
23
The Respiratory
System

An Introduction to 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
the production of sound.

• 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.

• 23-7 Summarize the physical principles governing
the movement of air into 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.

• 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.

• The Respiratory System
• Cells produce energy
• For maintenance, growth, defense, and division
• Through mechanisms that use oxygen and produce
carbon dioxide

• 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

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

• Organization of the Respiratory System
• The respiratory system is divided into:
• Upper respiratory system - above the larynx
• Lower respiratory system - below the larynx

• 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

Figure 23-1 The Components of the Respiratory System
Nasal cavity
Internal nares
Pharynx
Sphenoidal sinus
Esophagus
Clavicle
UPPER
RESPIRATORY
SYSTEM
LOWER
RESPIRATORY
SYSTEM
RIGHT
LUNG
Bronchioles
Bronchus
Trachea
Larynx
Hyoid bone
Tongue
Nose
Nasal conchae
Ribs Diaphragm
LEFT
LUNG
RIGHT
LUNG
Frontal sinus

• 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)

• The Respiratory Mucosa
• Consists of:
• An epithelial layer
• An areolar layer called the lamina propria
• Lines the conducting portion of 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

Figure 23-2a The Respiratory Epithelium of the Nasal Cavity and Conducting System
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.
Superficial view SEM × 1647

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
A diagrammatic view of the
respiratory epithelium of the
trachea, indicating the direction
of mucus transport inferior to
the pharynx.

Figure 23-2c The Respiratory Epithelium of the Nasal Cavity and Conducting System
The sectional appearance of
the respiratory epithelium, a
pseudostratified ciliated columnar
epithelium.
Stem cell
Basement
membrane
Mucous cell
Nucleus of
columnar
epithelial cell
Lamina
propria
Cilia

• 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

• Alveolar Epithelium
• Is a very delicate, simple squamous epithelium
• Contains scattered and specialized cells
• Lines exchange surfaces of alveoli

• The Respiratory Defense System
• Consists of a series of filtration mechanisms
• Removes particles and pathogens

• 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

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

• 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

• 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

• 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

• 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

Figure 23-3a Structures of the Upper Respiratory System
Dorsum
nasi
Apex
Nasal
cartilages
External
nares
The nasal cartilages and external
landmarks on the nose

Figure 23-3b Structures of the Upper Respiratory System
A frontal section through the head, showing
the meatuses and the maxillary sinuses and
air cells of the ethmoidal labyrinth
Tongue
Inferior meatus
Inferior nasal
concha
Maxillary sinus
Middle meatus
Middle nasal
concha
Superior
meatus
Superior
nasal concha
Lens
Right eye
Frontal sinus
Cranial cavityEthmoidal
air cell
Medial rectus
muscle
Lateral rectus
muscle
Nasal septum
Hard palate
Vomer
Perpendicular
plate of ethmoid
Mandible

Figure 23-3c Structures of the Upper Respiratory System
Nasal cavity
Internal nares
Nasopharynx
Pharyngeal tonsil
Pharynx
Oropharynx
Laryngopharynx
Epiglottis
Entrance to auditory tube
Glottis
Vocal fold
Esophagus
The nasal cavity and pharynx, as seen in sagittal
section with the nasal septum removed
Thyroid gland
Trachea
Cricoid cartilage
Thyroid cartilage
Hyoid bone
Lingual tonsil
Mandible
Palatine tonsil
Soft palate
Oral cavity
Tongue
Hard palate
External nares
Nasal vestibule
Inferior
Middle
Superior
Nasal conchae
Frontal sinus

• 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

• 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

23-3 The Larynx
• Air Flow
• From the pharynx enters the larynx
• A cartilaginous structure that surrounds the
glottis, which is a narrow opening

23-3 The Larynx
• Cartilages of the Larynx
• Three large, unpaired cartilages form the larynx
1. Thyroid cartilage
2. Cricoid cartilage
3. Epiglottis

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

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

23-3 The Larynx
• The Epiglottis
• Composed of elastic cartilage
• Ligaments attach to thyroid cartilage and hyoid
bone

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

23-3 The Larynx
• The Larynx Contains Three Pairs of Smaller
Hyaline Cartilages
1. Arytenoid cartilages
2. Corniculate cartilages
3. Cuneiform cartilages

Figure 23-4a The Anatomy of the Larynx
Epiglottis
Lesser cornu
Hyoid bone
Thyrohyoid
ligament
Laryngeal
prominence
Thyroid
cartilage
Cricothyroid
ligament
Cricoid cartilage
Cricotracheal
ligament
Tracheal
cartilages
Anterior view
Trachea
Larynx

Figure 23-4b The Anatomy of the Larynx
Epiglottis
Thyroid
cartilage
Tracheal
cartilages
Posterior view
Vestibular
ligament
Vocal
ligament
Arytenoid
cartilage

Figure 23-4c The Anatomy of the Larynx
Vestibular
ligament
Vocal
ligament
Arytenoid
cartilage
Cricothyroid
ligament
Cricotracheal
ligament
Sagittal section
ANTERIOR POSTERIOR
Epiglottis
Hyoid bone
Thyroid
cartilage
Corniculate
cartilage
Cricoid
cartilage
Tracheal
cartilages

23-3 The Larynx
• Cartilage Functions
• Corniculate and arytenoid cartilages function in:
• Opening and closing of glottis
• Production of sound

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

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

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

Figure 23-5a The Glottis and Surrounding Structures
Corniculate cartilage
Glottis in the open position.
Glottis (open)
POSTERIOR
ANTERIOR
Aryepiglottic
fold
Cuneiform cartilage
Vestibular fold
Vocal fold
Epiglottis
Root of tongue

Figure 23-5b The Glottis and Surrounding Structures
Glottis in the closed position.
Root of tongue
Epiglottis
Vocal fold
Vestibular fold
Glottis (closed)
POSTERIOR
ANTERIOR

Figure 23-5c The Glottis and Surrounding Structures
This photograph is a
representative laryngoscopic
view. For this view the camera
is positioned within the oro-
pharynx, just superior to the
larynx.
Root of tongue
Epiglottis
Vocal fold
Vestibular fold
Cuneiform cartilage
in aryepiglottic fold
Glottis (open)

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

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

Figure 23-6b The Anatomy of the Trachea
A cross-sectional view
The trachea
Lumen of
trachea
Tracheal
cartilage
Respiratory
epithelium
Thyroid
gland
Trachealis
muscle
Esophagus
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

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

Figure 23-6a The Anatomy of the Trachea
Hyoid
bone
Larynx
Trachea
Root of
right lung
Tracheal
cartilages
Location of carina
(internal ridge)
Lung
tissue
Root of
left lung
Primary
bronchi
Secondary
bronchi
RIGHT LUNG 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
ANIMATION Respiration: Respiratory Tract

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

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

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

Figure 23-7a The Gross Anatomy of the Lungs
Superior lobe
RIGHT LUNG
Horizontal fissure
Middle lobe
Inferior lobe
Oblique fissure
Thoracic cavity, anterior view
Liver,
right lobe
Liver,
left lobe
Boundary between
right and left
pleural cavities
Superior lobe
LEFT LUNG
Oblique fissure
Fibrous layer
of pericardium
Inferior lobe
Falciform ligament
Cut edge of
diaphragm

Figure 23-7b The Gross Anatomy of the Lungs
ApexApex
Superior lobe
Oblique
fissure
Inferior
lobe
Base
Left lung
The cardiac
notch
accommodates
the pericardial
cavity, which
sits to the left of
the midline.
Right lung
Superior
lobe
Middle
lobe
Inferior
lobe
Horizontal fissure
Oblique fissure
Base
The curving anterior and
lateral surfaces of each lung
follow the inner contours of
the rib cage.
Lateral Surfaces

Figure 23-7c The Gross Anatomy of the Lungs
Medial Surfaces
The medial surfaces, which contain the
hilium, have more irregular shapes. The
medial surfaces of both lungs bear
grooves that mark the positions of
the great vessels and the heart.
Apex
Superior
lobe
Pulmonary artery
Pulmonary veins
Horizontal fissure
Oblique fissure Inferior
lobe
Middle
lobe
Right lung Left lung
Base Base
Inferior
lobe
Apex
Superior
lobe
Groove
for aorta
Pulmonary
artery
Pulmonary
veins
Oblique
fissure
The hilium of the
lung is a groove
that allows
passage of the
primary bronchi,
pulmonary
vessels, nerves,
and lymphatics.
Diaphragmatic
surface

Figure 23-8 The Relationship between the Lungs and Heart
Pericardial
cavity
Right lung,
middle lobe
Oblique fissure
Right pleural
cavity
Atria
Esophagus
Aorta
Right lung,
inferior lobe
Spinal cord
Left lung,
inferior lobe
Mediastinum
Bronchi
Parietal pleura
Left pleural cavity
Visceral pleural
Left lung,
superior lobe
Ventricles
Body of sternum
Rib

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

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

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

23-5 The Lungs
• Bronchitis
• Inflammation of bronchial walls
• Causes constriction and breathing difficulty

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

23-5 The Lungs
• Autonomic Control
• Regulates smooth muscle
• Controls diameter of bronchioles
• Controls airflow and resistance in lungs

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)

23-5 The Lungs
• Asthma
• Excessive stimulation and bronchoconstriction
• Stimulation severely restricts airflow

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)

Figure 23-9a The Bronchi and Lobules of the Lung
Bronchopulmonary
segment
Respiratory
bronchiole
Terminal
bronchiole
Bronchioles
Smaller
bronchi
Alveoli in a
pulmonary
lobule
Tertiary bronchi
Secondary
bronchus
Visceral pleura
Left primary
bronchus
Trachea
Cartilage plates
The branching pattern of
bronchi in the left lung,
simplified

Figure 23-9b The Bronchi and Lobules of the Lung
Respiratory
epithelium
Bronchiole
Bronchial artery (red),
vein (blue), and
nerve (yellow)
Terminal
bronchiole
Respiratory
bronchiole
Elastic fibers
Capillary
bedsBranch of
pulmonary
vein
Alveolar
duct
Arteriole
Lymphatic
vessel
Alveoli
Alveolar sac
Interlobular
septum
Visceral pleura
Pleural cavity
Parietal pleura
The structure of a single pulmonary lobule, part of a
bronchopulmonary segment
Branch of
pulmonary
artery
Smooth muscle
around terminal
bronchiole

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

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

Figure 23-10a Respiratory Tissue
Respiratory
bronchiole
Alveoli
Alveolar
sac
Arteriole
Alveolarduct
Histology of the lung LM × 14
Low power micrograph of lung
tissue

Figure 23-10b Respiratory Tissue
SEM of lung tissue showing the
appearance and organization of the alveoli
Alveolar
sac
Alveoli
Alveolar
duct
SEM × 125Lung tissue

23-5 The Lungs
• Alveolar Epithelium
• Consists of simple squamous epithelium
• Consists of thin, delicate pneumocytes type I
• Patrolled by alveolar macrophages (dust cells)
• Contains pneumocytes type II (septal cells) that
produce surfactant

23-5 The Lungs
• Surfactant
• Is an oily secretion
• Contains phospholipids and proteins
• Coats alveolar surfaces and reduces surface
tension

Figure 23-11a Alveolar Organization
Smooth muscle
Elastic fibers
Capillaries
Respiratory bronchiole
Alveolar duct
Alveolus
Alveolar
sac
The basic structure of a portion of a single
lobule.

Figure 23-11b Alveolar Organization
Pneumocyte
type I
Alveolar
macrophage
Pneumocyte
type II
Elastic
fibers
Capillary
Alveolar macrophage
A diagrammatic view of alveolar structure. A single capillary may
be involved in gas exchange with several alveoli simultaneously.
Endothelial
cell of capillary

23-5 The Lungs
• Respiratory Distress Syndrome
• Difficult respiration
• Due to alveolar collapse
• Caused when pneumocytes type II do not produce
enough surfactant
• Respiratory Membrane
• The thin membrane of alveoli where gas exchange
takes place

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

Figure 23-11c Alveolar Organization
0.5 µm
Fused
basement
membrane
Alveolar
epithelium
Surfactant
Nucleus of
endothelial cell
Capillary
endothelium
Red blood cell
Capillary lumen
Alveolar air space
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

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)

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

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

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)

23-5 The Lungs
• The Pleura
• Consists of two layers
1. Parietal pleura
2. Visceral pleura
• Pleural fluid
• Lubricates space between two layers

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

• 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

Figure 23-12 An Overview of the Key Steps in Respiration
Respiration
External Respiration
Pulmonary
ventilation
Gas
diffusion
O2 transport
Gas
diffusion
Tissues
Gas
diffusion
Gas
diffusion
CO2 transport
Lungs
Internal Respiration

• Abnormal External Respiration Is Dangerous
• Hypoxia
• Low tissue oxygen levels
• Anoxia
• Complete lack of oxygen

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

• 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

Figure 23-13 Gas Pressure and Volume Relationships

Figure 23-13a Gas Pressure and Volume Relationships
If you decrease the volume
of the container, collisions
occur more frequently per
unit time, elevating the
pressure of the gas.

Figure 23-13b Gas Pressure and Volume Relationships
If you increase the volume,
fewer collisions occur per
unit 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 declines.

• 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)

• Pulmonary Ventilation
• Causes volume changes that create changes in
pressure
• Volume of thoracic cavity changes
• With expansion or contraction of diaphragm or rib
cage

Figure 23-14a Mechanisms of Pulmonary Ventilation
Ribs and
sternum
elevate
Diaphragm
contracts
As the rib cage is elevated or
the diaphragm is depressed,
the volume of the thoracic
cavity increases.

Figure 23-14b Mechanisms of Pulmonary Ventilation
Diaphragm
Pleural
cavity
Cardiac
notch
At rest.
Pressure outside and inside are
equal, so no air movement occurs
Poutside = Pinside

Figure 23-14c Mechanisms of Pulmonary Ventilation
Poutside > Pinside
Volume increases
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.
Pressure inside falls, so air flows in

Figure 23-14d Mechanisms of Pulmonary Ventilation
Poutside < Pinside
Volume decreases
Pressure inside rises, so air flows out
Exhalation. When the rib cage
returns to its original position
and the diaphragm relaxes, the
volume of the thoracic cavity
decreases. Pressure rises, and
air moves out of the lungs.

• 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

• Pressure Changes during Inhalation and
Exhalation
• Can be measured inside or outside the lungs
• Normal atmospheric pressure
• 1 atm = 760 mm Hg
ANIMATION Respiration: Pressure Gradients

• 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

• Maximum Intrapulmonary Pressure
• Maximum straining, a dangerous activity, can
increase range
• From −30 mm Hg to +100 mm Hg

• 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

Table 23-1 The Four Most Common Methods of Reporting Gas Pressures

• 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

• Injury to the Chest Wall
• Pneumothorax allows air into pleural cavity
• Atelectasis (also called a collapsed lung) is a
result of pneumothorax

Figure 23-15 Pressure and Volume Changes during Inhalation and Exhalation
Trachea
Bronchi
Lung
Diaphragm
Right pleural
cavity
Left pleural
cavity
Intrapulmonary
pressure
(mm Hg)
Intrapleural
pressure
(mm Hg)
Tidal
volume
(mL)
Changes in
intrapulmonary
pressure during a
single respiratory cycle
Changes in intrapleural
pressure during a
A plot of tidal volume,
the amount of air
moving into and out of
the lungs during a
Time (sec)
INHALATION EXHALATION

• The Respiratory Muscles
• Most important are:
• The diaphragm
• External intercostal muscles of the ribs
• Accessory respiratory muscles
• Activated when respiration increases significantly

• The Mechanics of Breathing
• Inhalation
• Always active
• Exhalation
• Active or passive

• Muscles Used in Inhalation
• Diaphragm
• Contraction draws air into lungs
• 75% of normal air movement
• External intercostal muscles
• Assist inhalation
• 25% of normal air movement
• Accessory muscles assist in elevating ribs
• Sternocleidomastoid
• Serratus anterior
• Pectoralis minor
• Scalene muscles

Figure 23-16a The Respiratory Muscles
Diaphragm
contracts
Ribs and
sternum
elevate
Movements of the ribs and diaphragm
that increase the volume of the thoracic
cavity. Diaphragmatic movements were
also illustrated in Figure 23–14.

Figure 23-16b The Respiratory Muscles
Accessory Muscles
of Inhalation
Sternocleidomastoid
muscle
Scalene muscles
Pectoralis minor
muscle
Serratus anterior
muscle
Primary Muscle
of Inhalation
Diaphragm
Internal oblique
muscle
Rectus abdominus
External oblique
muscle
Transversus thoracis
muscle
Internal intercostal
muscles
Accessory Muscles
of Exhalation
Primary Muscle of Inhalation
External intercostal muscles
An anterior view at rest (with no
air movement), showing the
primary and accessory
respiratory muscles.

Figure 23-16c The Respiratory Muscles
Primary Muscle
of Inhalation
Inhalation. A lateral view during inhalation,
showing the muscles that elevate the ribs.
Sternocleidomastoid
muscle
Accessory Muscle
of Inhalation
(active when needed)
Scalene muscles
Pectoralis minor muscle
Serratus anterior muscle
External intercostal muscles
Diaphragm

• Muscles Used in Exhalation
• Internal intercostal and transversus thoracis muscles
• Depress the ribs
• Abdominal muscles
• Compress the abdomen
• Force diaphragm upward

Figure 23-16d The Respiratory Muscles
Exhalation. A lateral view during
exhalation, showing the muscles that
depress the ribs. The abdominal muscles
that assist in exhalation are represented by a
single muscle (the rectus abdominis).
Rectus abdominis and
other abdominal
muscles (not shown)
Internal intercostal
muscles
Transversus thoracis
muscle
Accessory Muscles
of Exhalation
(active when needed)

• Modes of Breathing
• Respiratory movements are classified
• By pattern of muscle activity
• Quiet breathing
• Forced breathing

• 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

• Elastic Rebound
• When inhalation muscles relax
• Elastic components of muscles and lungs recoil
• Returning lungs and alveoli to original position

• Forced Breathing (Hyperpnea)
• Involves active inhalation and exhalation
• Assisted by accessory muscles
• Maximum levels occur in exhaustion

• 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)

• The Respiratory Minute Volume (VE)
• Amount of air moved per minute
• Is calculated by:
respiratory rate × tidal volume
• Measures 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

• Alveolar Gas Content
• Alveoli contain less O2, more CO2 than
atmospheric air
• Because air mixes with exhaled air

• 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

• 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. Resting tidal volume (Vt)
2. Expiratory reserve volume (ERV)
3. Residual volume
4. Inspiratory reserve volume (IRV)

• 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

• 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

• Four Calculated Respiratory Capacities
4. Total lung capacity
• Vital capacity + residual volume
• Pulmonary Function Tests
• Measure rates and volumes of air movements

Figure 23-17 Pulmonary Volumes and Capacities
Pulmonary Volumes and Capacities (adult male)
Resting
tidal volume
(VT = 500 mL)
Inspiratory
reserve
volume (IRV)
Inspiratory
capacity
Vital
capacity
Total lung
capacity
Expiratory
reserve
volume (ERV)
Residual
volume
Functional
residual
capacity
(FRC)
Minimal volume
(30–120 mL)
Time
0
1200
2200
2700
Volume(mL)
6000

Figure 23-17 Pulmonary Volumes and Capacities
Gender Differences
Vital
capacity
Males Females
Total lung capacity 6000 mL 4200 mL
Residual volume 1200Residual volume 1200
Inspiratory
capacity
Functional
residual
capacity
IRV 3300 1900
500500VT
ERV 1000 700
1100

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

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

23-8 Gas Exchange
• Dalton’s Law and Partial Pressures
• Composition of Air
• Nitrogen (N2) is about 78.6%
• Oxygen (O2) is about 20.9%
• Water vapor (H2O) is about 0.5%
• Carbon dioxide (CO2) is about 0.04%

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)

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

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

Figure 23-18 Henry’s Law and the Relationship between Solubility and Pressure

Figure 23-18a Henry’s Law and the Relationship between Solubility and Pressure
Increasing the pressure drives gas molecules
into solution until an equilibrium is established.
Example
Soda is put into
the can under
pressure, and
the gas (carbon
dioxide) is in
solution at
equilibrium.

Figure 23-18b Henry’s Law and the Relationship between Solubility and Pressure
When the gas pressure decreases, dissolved
gas molecules leave the solution until a new
equilibrium is reached.
Example
Opening the
can of soda
relieves the
pressure,
and bubbles
form as the
dissolved gas
leaves the
solution.

23-8 Gas Exchange
• Solubility in Body Fluids
• CO2 is very soluble
• O2 is less soluble
• N2 has very low solubility

23-8 Gas Exchange
• Normal Partial Pressures
• In pulmonary vein plasma
• PCO
2
= 40 mm Hg
• PO
2
= 100 mm Hg
• PN
2
= 573 mm Hg

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

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

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

23-8 Gas Exchange
• Partial Pressures in the Systemic Circuit
• Oxygenated blood mixes with deoxygenated blood
from conducting passageways
• Lowers the PO
2
of blood entering systemic circuit
(drops to about 95 mm Hg)

23-8 Gas Exchange
• Partial Pressures in the Systemic Circuit
• Interstitial Fluid
• PO
2
40 mm Hg
• PCO
2
45 mm Hg
• Concentration gradient in peripheral capillaries is
opposite of lungs
• CO2 diffuses into blood
• O2 diffuses out of blood

Figure 23-19a An Overview of Respiratory Processes and Partial Pressures in Respiration
Systemic
circuit
Pulmonary
circuit
Alveolus
Respiratory
membrane
Pulmonary
capillary
External Respiration
Systemic
circuit
O = 100P 2
CO2 40=P
O = 100P 2
CO2 40=P
O = 40P 2
CO2 45=P
CO2
O2

Figure 23-19b An Overview of Respiratory Processes and Partial Pressures in Respiration
Internal Respiration
Interstitial fluid
Systemic
capillary
O = 95P 2
CO2 40=P
CO
2
O
2
Systemic
circuit
Pulmonary
circuit
Systemic
circuit
CO2 45=P
O = 40P 2
O = 40P 2
CO2 45=P

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

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

23-9 Gas Transport
• Hemoglobin Saturation
• The percentage of heme units in a hemoglobin
molecule that contain bound oxygen
• Environmental Factors Affecting Hemoglobin
• PO
2
of blood
• Blood pH
• Temperature
• Metabolic activity within RBCs

23-9 Gas Transport
• Oxygen–Hemoglobin Saturation Curve
• A graph relating the saturation of hemoglobin to partial
pressure of oxygen
• Higher PO
2
results in greater Hb saturation
• 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

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

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

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

Figure 23-20 An Oxygen-Hemoglobin Saturation Curve
Oxyhemoglobin(%saturation)
% saturation
of Hb(mm Hg)
PO2
10
20
30
40
50
60
70
80
90
100
13.5
35
57
75
83.5
89
92.7
94.5
96.5
97.5
(mm Hg)PO2

23-9 Gas Transport
• Hemoglobin and pH
• Bohr effect is the result of pH on hemoglobin-saturation
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

Figure 23-21a The Effects of pH and Temperature on Hemoglobin Saturation
Effect of pH. When the pH drops 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.
7.6
7.4
7.2
P (mm Hg)O2

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

Figure 23-21b The Effects of pH and Temperature on Hemoglobin Saturation
Effect of temperature. When the
temperature rises, more oxygen is
released; the oxygen–hemoglobin
saturation curve shifts to the right.
10°C 20°C
38°C
43°C
(mm Hg)PO2

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

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

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

Figure 23-22 A Functional Comparison of Fetal and Adult Hemoglobin
Fetal hemoglobin
Adult hemoglobin
PO2
(mm Hg)

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

23-9 Gas Transport
• Carbonic Acid Formation
• 70% 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

23-9 Gas Transport
• CO2 Binding to Hemoglobin
• 23% is bound to amino groups of globular proteins in Hb
molecule
• Forming carbaminohemoglobin
• Transport in Plasma
• 7% is transported as CO2 dissolved in plasma

Figure 23-23 Carbon Dioxide Transport in Blood
CO2 diffuses
into the
bloodstream
93% diffuses
into RBCs
23% binds to Hb,
forming
carbaminohemoglobin,
Hb•CO2
H+
removed
by buffers,
especially Hb
70% converted to
H2CO3 by carbonic
anhydrase
7% remains
dissolved in
plasma (as CO2)
H2CO3 dissociates
into H+
and HCO3
−
HCO3
−
moves
out of RBC in
exchange for
Cl−
(chloride
shift)
RBC
PLASMA

Figure 23-24 A Summary of the Primary Gas Transport Mechanisms
Plasma
Red blood cell
Alveolar
air space
O2 pickup
Pulmonary
capillary
O2 delivery
Alveolar
air space
Pulmonary
capillary
Systemic
capillary
CO2 delivery
Systemic
capillary
Red blood cell
Cells in
peripheral
tissues
Cells in
peripheral
tissues
Chloride
shift
CO2 pickup

Plasma
Red blood cell
Alveolar
air space
O2 pickup
Pulmonary
capillary

O2 delivery
Systemic
capillary
Red blood cell
Cells in
peripheral
tissues

Alveolar
air space
Pulmonary
capillary
CO2 delivery

Systemic
capillary
Cells in
peripheral
tissues
Chloride
shift
CO2 pickup

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

• Local Regulation of Gas Transport and Alveolar Function
• Rising PCO
2
levels
• Relax smooth muscle in arterioles and capillaries
• Increase blood flow
• Coordination of lung perfusion and alveolar ventilation
• Shifting blood flow
• PCO
2
levels
• Control bronchoconstriction and bronchodilation

• 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

• 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

• 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)

• 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

• Quiet Breathing
• Brief activity in the DRG
• Stimulates inspiratory muscles
• DRG neurons become inactive
• Allowing passive exhalation

Figure 23-25a Basic Regulatory Patterns of Respiration
Quiet Breathing
INHALATION
(2 seconds)
Diaphragm and external
intercostal muscles
contract and inhalation
occurs.
Dorsal
respiratory
group
inhibited
Dorsal
respiratory
group active
Diaphragm and
external intercostal
muscles relax and
passive exhalation
occurs.
EXHALATION
(3 seconds)

• Forced Breathing
• Increased activity in DRG
• Stimulates VRG
• Which activates accessory inspiratory muscles
• After inhalation
• Expiratory center neurons stimulate active exhalation

Figure 23-25b Basic Regulatory Patterns of Respiration
INHALATION
DRG and
inspiratory
center of VRG
are active.
Expiratory center
of VRG is
inhibited.
DRG and
inspiratory
center of VRG
are inhibited.
Expiratory
center of VRG
is active.
Forced Breathing
Muscles of inhalation
contract, and opposing
muscles relax
Inhalation occurs,
EXHALATION
Muscles of inhalation
relax and muscles of
exhalation contract.
Exhalation occurs.

• 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

• Respiratory Centers and Reflex Controls
• Interactions between VRG and DRG
• Establish basic pace and depth of respiration
• The pneumotaxic center
• Modifies the pace

Figure 23-26 Control of Respiration
Respiratory Centers and Reflex Controls
The locations and
relationships
between the major
respiratory centers in
the pons and medulla
oblongata and other
factors important to
the reflex control of
respiration. Pathways
for conscious control
over respiratory
muscles are not
shown.
Pneumotaxic
center
HIGHER CENTERS
Cerebral cortex
Limbic system
Hypothalamus
Cerebrum
CSF
CHEMORECEPTORSPons
Apneustic
center
Medulla
oblongata
KEY
= Stimulation
= Inhibition

Figure 23-26 Control of Respiration
KEY
= Stimulation
= Inhibition
Motor neurons
controlling other
respiratory muscles
Respiratory Centers and Reflex Controls
N IX and N X
Chemoreceptors and
baroreceptors of carotid
and aortic sinuses
Diaphragm
Stretch
receptors
of lungs
N X
Spinal
cord
Motor neurons
controlling
diaphragm
Medulla
oblongata
Respiratory Rhythmicity
Centers
Dorsal respiratory
group (DRG)
Ventral respiratory
group (VRG)
Phrenic nerve

• Sudden Infant Death Syndrome (SIDS)
• Disrupts normal respiratory reflex pattern
• May result from connection problems between
pacemaker complex and respiratory centers

• 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

• 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

• The glossopharyngeal nerve
• From carotid bodies
• Stimulated by changes in blood pH or PO
2
• The vagus nerve
• From aortic bodies
• Stimulated by changes in blood pH or PO
2

• Central chemoreceptors that monitor
cerebrospinal fluid
• Are on ventrolateral surface of medulla oblongata
• Respond to PCO
2
and pH of CSF

• Chemoreceptor Stimulation
• Leads to increased depth and rate of respiration
• Is subject to adaptation
• Decreased sensitivity due to chronic stimulation

• Hypercapnia
• An increase in arterial PCO
2
• Stimulates chemoreceptors in the medulla
oblongata
• To restore homeostasis

• 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
2
(hypocapnia)
• Stimulates chemoreceptors to decrease respiratory rate

Figure 23-27a The Chemoreceptor Response to Changes in PCO2
HOMEOSTASIS
Normal
arterial PCO2
HOMEOSTASIS
RESTORED
Increased respiratory
rate with increased
elimination of CO2 at
alveoli
Stimulation of CSF
chemoreceptors at
medulla oblongata
HOMEOSTASIS
DISTURBED
Increased PCO2
,
decreased pH
in CSF
Stimulation
of arterial
chemoreceptors
Stimulation of
respiratory muscles
Start
Normal
arterial PCO2
Increased
arterial PCO2
(hypocapnia)
Increased
arterial PCO2

Figure 23-27b The Chemoreceptor Response to Changes in PCO2
HOMEOSTASIS
Normal
arterial PCO2
Normal
arterial PCO2
HOMEOSTASIS
RESTORED
Start
Decreased respiratory
rate with decreased
elimination of CO2 at
alveoli
Reduced stimulation
of CSF chemoreceptors
Inhibition of
respiratory muscles
Inhibition of arterial
chemoreceptors
Decreased PCO2
,
increased pH
in CSF
Decreased
arterial PCO2
(hypocapnia)
HOMEOSTASIS
DISTURBED
Decreased
arterial PCO2

• 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

• 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

• 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

• 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

• 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

• 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

• 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

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)

Figure 23-28 Decline in Respiratory Performance with Age and Smoking
Regular
smoker
Disability
Death
Age (years)
Stopped
at age 65
Stopped
at age 45
Never smoked
Respiratoryperformance
(%ofvalueatage25)

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

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

Figure 23-29 System Integrator: The Respiratory System
The RESPIRATORY System
CardiovascularEndocrineNervousMuscularSkeletal
Protects portions of upper respiratory
tract; hairs guard entry to external
nares
Integumentary
Body System Respiratory System Respiratory System Body System
S Y S T E M I N T E G R A T O R
Cardiovascular
Page759
Endocrine
Page632
Nervous
Page543
Muscular
Page369
Skeletal
Page275
Integumentary
Page165Page910Page992
Digestive
Page1072
UrinaryReproductive
Lymphatic
Movements of ribs important in
breathing; axial skeleton surrounds
and protects lungs
Muscular activity generates carbon
dioxide; respiratory muscle fill and
empty lungs; other muscles control
entrances to respiratory tract; intrinsic
laryngeal muscles control airflow
through larynx and produce sounds
Monitors respiratory volume and
blood gas levels; controls pace and
depth of respiration
Epinephrine and norepinephrine
stimulate respiratory activity and
dilate respiratory passageways
Circulates the red blood cells that
transport oxygen and carbon
dioxide between lungs and
peripheral tissues
Tonsils protect against
infection at entrance to
respiratory tract;
lymphatic vessels monitor lymph
drainage from lungs and mobilize
adaptive defenses when infection occurs
The respiratory system provides oxygen
and eliminates carbon dioxide for our
cells. Stabilizing the concentrations of
these gases involves a continual
exchange of materials with the outside
world. The respiratory system is
therefore crucial to maintaining
homeostasis for all body systems.
Page807
Lymphatic
Provides oxygen to nourish tissues
and removes carbon dioxide
Provides oxygen to skeletal
structures and disposes of carbon
dioxide
Provides oxygen needed for
muscle contractions and disposs
of carbon dioxide generated by
active muscles
Provides oxygen needed for neural
activity and disposes of carbon
dioxide
Angiotensin-converting enzyme
(ACE) from capillaries of lungs
converts angiotensin I to
angiotensin II
Bicarbonate ions contribute to
buffering capability of blood;
activation of angiotensin II by
ACE important in regulation of
blood pressure and volume
Alveolar phagocytes present
antigens to trigger specific
defenses; mucous membrane
lining the nasal cavity and
upper pharynx traps pathogens,
protects deeper tissues

169 Ch 23_lecture_presentation

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169 Ch 23_lecture_presentation