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Respiratory System
Function
– Supply cells with
oxygen
– Get rid of waste;
carbon dioxide
Respiration
Five Stages
– Pulmonary Ventilation
Inhaling and exhaling
– Gas Exchange
Between respiratory cells and blood
– Transport
Of gases throughout the body by the blood
Respiration
Five Stages (cont.)
– Exchange
Of gases between blood and tissue cells (internal
respiration)
– Cellular Respiration
Use of oxygen by body cells to break down
glucose and release energy (ATP) and carbon
dioxide
Upper Respiratory Tract
Nose
– External nose
structures
lateral
cartilage
– External nares
lesser alar
cartilages
greater alar
cartilage
dense
fibrous
connective
tissue
Upper Respiratory Tract
Nasal Cavity
superior concha
ethmoid
– Septum
– Roof
– Floor
middle
sphenoid
concha
nasal
bone
septal
cartilage
Nasal conchae
Internal nares
(choanae)
Mucosa
vomer
palatine
inferior
bone
concha
palatine
process
internal
nares
Upper Respiratory Tract
Paranasal Sinuses
frontal
sinus
– 4 pair
maxillary
sinus
sphenoid
sinus
ethmoid
sinus
Upper Respiratory Tract
Pharynx
– Nasopharynx
– Oropharynx
– Laryngopharynx
nasopharynx
oropharynx
laryngopharynx
Lower Respiratory Tract
epiglottis
Larynx
– Cartilages
Thyroid
 Laryngeal
prominence
Cricoid
Arytenoid
Corniculate
Cuneiform
Epiglottic
cuneiform
cartilage
thyroid
cartilage
corniculate
cartilage
laryngeal
arytenoid
prominence
cartilage
cricoid
cartilage
Lower Respiratory Tract
Internal Structures
epiglottis
– Auditus
– Vestibule
– Vestibular folds
– Ventricles
vestibular
folds
vocal
folds
– Vocal folds
– Glottis
glottis
Lower Respiratory Tract
Laryngeal Muscles
– Cricothyroid
Posterior
cricoarytenoideus
Lateral
cricoarytenoideus
Thyroarytenoideus
Vocalis
Aryepiglottic
thyroarytenoideus
aryepiglottic
vocalis
lateral
cricothyroid
posterior
cricoarytenoideus
cricoarytenoideus
Lower Respiratory Tract
Sound Production
– Pitch
– Volume
Lower Respiratory Tract
Trachea
– Tracheal cartilages
and carina
– Lined with
pseudostratified
ciliated columnar
epithelium
– Goblet cells
– Horseshoe shaped
hyaline cartilage
– Trachealis muscle
posterior
esophagus
trachealis
muscle
hyaline
cartilage
Pseudostratified
ciliated
columnar
epithelium
adventitia
Bronchial Tree
Primary Bronchi
– Rt. Bronchus is
shorter, wider and
steeper than the left
– Same wall structure as
trachea
– Cartilage in plates in
smaller passageways
– Branch into secondary
and tertiary bronchi
(R) primary
bronchus
(L) primary
bronchus
Bronchial Tree
Trachea  (R) and (L) primary
bronchi  secondary (lobar)
bronchi  tertiary (segmental)
bronchi  smaller bronchi 
bronchioles  terminal
(R) primary
bronchus
bronchioles  respiratory
bronchioles  alveolar duct 
alveolar sac  alveolus
(L) primary
bronchus
trachea
Bronchial Tree
Bronchioles
– No cartilage
– No cilia or mucous
producing cells
– Epithelium changes to
simple columnar
Terminal Bronchioles
– Simple cuboidal
epithelium
– Lead into respiratory
bronchioles
terminal
bronchiole
Bronchial Tree
Respiratory Bronchioles
alveoli
– Lead into alveolar ducts
Alveoli
– Simple squamous
epithelium
– May open into an alveolar
sac
– Where gas exchange takes
place capillaries
alveolar
sac
respiratory
bronchiole
Alveoli
Septal Cells (type II alveolar cells)
– Produce pulmonary surfactant
Dust Cells
– Macrophages in alveoli
– Phagocytize bacteria, dirt, foreign
particles
Respiratory Membrane=
– Squamous alveoli epithelium +
alveolar basement membrane +
endothelium of capillary walls
– Gas on one side, blood on other
– Gas diffuses easily
The Lungs
Fill pleural cavities
lateral to mediastinum
apex
Anatomical Structures
Apex
Hilus
Base
Costal surface
Pleura
Serous
membranes
Parietal
Visceral
Pleural cavity
Pleural
fluid
base
Right Lung
The Lungs
SUPERIO
R LOBE
– 3 lobes
Superior, middle,
inferior
– Oblique and horizontal
fissures
SUPERIOR
LOBE
oblique
fissure
horizontal
fissure
 Left Lung
 2 lobes
 Superior,
inferior
 Oblique fissure
 Cardiac notch
 Lingula
MIDDLE LOBE
cardiac
INFERIOR
notch
LOBE
oblique
INFERIOR
fissure
LOBE
Bronchopulmonary Segments
Each lung has 10
segments (some list only 8
in the left lung)
Each segment is served by
a tertiary (segmental)
bronchus, an artery and
vein
Help to reduce spread of
disease or infection
ANTERIOR
VIEW
Blood Supply
Bronchial Circulation (to lungs)
– Bronchial Arteries
Arise from aorta
Run with bronchi
– Bronchial Veins
Drain blood from lung tissue
Empty into the azygos and hemiazygos veins
Pulmonary circulation (to circulation)
Pulmonary trunk  pulmonary arteries  branch within lungs,
travel with bronchi  pulmonary capillaries  surround alveoli
 gas exchange  pulmonary veins  (L) atrium of heart
GasATMOSPHERIC
Pressures
PRESSURE
Intrapleural pressure
756 mm Hg (-4 mm Hg)
parietal pleura
Collapsing
force of lungs
(4 mm Hg)
pleural cavity
visceral pleura
Intrapulmonary pressure
760 mm Hg (0 mm Hg)
Ventilation And Pressure
Ventilation
– Taking air in and out of lungs
– Inspiration, expiration
– Dependant upon difference in pressures in alveoli
and outside atmosphere
Intrapulmonary Pressure
– Within alveoli
– Changes during breathing
– Always equalizes with atmospheric pressure (760
mm hg at sea level)
Ventilation And Pressure
Intrapleural Pressure
– Within the pleural cavity
– Fluctuates
– Maintains 4 mm less pressure than in alveoli
(negative compared to atmospheric or intrapulmonary
pressures)
– Created by the thorax expanding faster than the lungs
in fetal development
***Any condition that equalizes intrapleural
pressure with intrapulmonary pressure will
cause lung collapse (atelectasis)
Forces Acting On Lungs
Forces pushing lungs out, towards the
thorax wall:
1. Greater pressure inside the lungs
(intrapulmonary pressure) than in the
surrounding pleural cavities (intrapleural
pressure)
2. Adhesive force created by the fluid in the
pleural cavity
3. Atmospheric pressure pushing in on the
thorax
Forces Acting On Lungs
Forces pulling lungs in, away from the
thorax wall
1. Tendency of elastic fibers in lungs to recoil
2. Surface tension within alveoli draw them
back to their smallest dimension
Inspiration And Expiration
Dependant upon the relationship between
change in volume or pressure
Boyle’s Law
– Pressure of gas varies inversely with its volume
(when temp. Is constant)
Inspiration
Expiration
Forced Expirations
Abdominal and internal intercostal
muscles contract (not used in normal
expiration)
Reduction in volume of thoracic cavity
More air expelled
Pulmonary Surfactant
Lipoprotein
Reduces surface tension (cohesive force
between water molecules) within alveoli
Produced by septal cells (type II alveolar cells)
Produced during last two months of fetal
development
Reduces energy required to stretch lungs
Helps prevent lung collapse
Resistance And Compliance
Airway Resistance
– Larger diameter = less
resistance
– Any factor that decreases
airway diameter will
increase energy needed to
breath
– Mucus, infections, tumors,
asthma
Compliance
– Ease in which lungs will
distend
– Amount of change in lung
volume that occurs with
change in intrapulmonary
pressure
– High compliance = lungs
and thorax easily
expandable
– Surfactant increases
compliance
Respiratory Volumes
Can be measured by a respirometer or
spirometer
Tidal Volume (TV)
– Amount of air inspired and expired during
normal breathing (usually 500 ml)
Residual Volume (RV)
– 1200 ml air remaining in lungs to prevent
collapse
Respiratory Capacities
Vital Capacity (VC)
– Maximum inspiration + maximum expiration
(4700 ml)
Reduced in restrictive disorders (fibrosis), but rate
of expiration is normal
Normal in obstructive disorders (asthma), but rate
of expiration is reduced
Dead Space
Anatomical Dead Space
– Air found in airways not undergoing gas
exchange (150 ml)
Physiological Dead Space
– Air available in alveoli but not used (due to
lack of blood, etc.)
Respiratory Volumes
Minute Respiratory Volume (MRV)
– Breathing rate/min. X tidal volume
– 12 breaths x 500 = 6000 ml
Alveolar Ventilation Rate (AVR)
– Measurement of incoming air actually used for
respiration
– Breathing rate x (tidal volume - dead space)
Gas Exchange
Dalton’s Law
– Each gas in a mixture will exert its own
pressure on a container equal to the amount
of pressure it would exert on its own
– Partial Pressure
Amt. of pressure exerted by each individual gas
in a mixture
Total pressure in a mixture = sum of all partial
pressures
– PN2 + PO2 + PCO2
Gas Exchange
Henry’s Law
– When a mixture of gases is in contact with a liquid,
each gas will dissolve into the liquid in proportion
to its partial pressure
– The higher the partial pressure of a gas, the faster
it will go into solution
Gas Solubility
– Also influences how readily gas will go into
solution
– Carbon dioxide is more soluble than oxygen
– Nitrogen is the least soluble gas in air
Gas Exchange
External Respiration
– Between alveoli and pulmonary capillaries
– Partial pressure of O2 is greater in the
alveoli
O2 diffuses into capillaries
– Partial pressure of CO2 is greater in
capillaries
CO2 diffuses out of capillaries into the alveoli
Gas Exchange
Internal Respiration
– Between blood and body cells
– Partial pressure of O2 is higher in blood
O2 diffuses into body cells
– CO2 partial pressure greater in body cells
CO2 diffuses into blood
Gas Transport
98% of oxygen in blood is associated with
hemoglobin
The affinity of hemoglobin to O2 is dependant
upon the partial pressure of O2
In Body Tissues
– Oxygen partial pressure is low
– Hemoglobin loses affinity for oxygen
– Releases oxygen
In Lungs
– High oxygen partial pressure
– Hemoglobin has a high affinity for oxygen
– Attaches to oxygen
Oxygen Transport
Factors affecting the affinity of hemoglobin to
oxygen
1. pH
Affinity decreases with decrease in pH
High CO2 can decrease pH
More oxygen released to body cells when CO2 levels are high
2. Temperature
Increased temperature causes a decreased affinity
Increase in cellular metabolism causes an increase temp.,
Partial pressure of CO2 and decrease in pH
Decreased affinity  more O2 released to body cells
Oxygen Transport
3.
DPG (2,3-diphosphoglyceric acid)
Released by RBC’s when O2 supply to body tissues is low
DPG reversibly binds to hemoglobin decreasing its affinity
to O2
Oxygen released to body tissues
–
Fetal hemoglobin has a much higher affinity for
oxygen than maternal hemoglobin
Maternal hemoglobin releases O2 to fetal hemoglobin
Carbon Dioxide Transport
3 Methods of CO2 Transport
1. Dissolved in plasma
7 to 10%
2.
Attached to hemoglobin
20 to 30%
Forms carbaminohemoglobin
3. As a bicarbonate ion (HCO3-)
60 to 70%
Catalyzed by carbonic anhydrase
Control Of Respiration
The brain and local factors in the lung work
together to regulate and coordinate
respiration
Local Factors
– Bronchiole smooth muscle is sensitive to
changes in CO2 concentration
Increased CO2  relaxes smooth muscle in
bronchioles  dilate  more CO2 released from
lungs
Opposite if CO2 levels decrease
Control of Respiration
Local Factors (cont.)
– Pulmonary arterioles are sensitive to changes
in O2 and H+ ions
Decrease in O2 or increase in H+  pulmonary
arterioles contract  blood shunted towards alveoli
with more O2
Just the opposite if O2 levels are high
Brain Control Of Respiration
Basic breathing pattern is
set by the reticular
formation in the medulla
and pons
Medulla Rhythmicity
Center
– Inspiratory Neurons
Cause contraction of
inspiratory muscles via
phrenic nerve and
intercostal nerves
Fire for 2 sec (inspiration)
Cease for 3 sec
(expiration)
Brain Control Of Respiration
Medulla Rhythmicity
Center (cont.)
– Expiratory Neurons
Inactive during normal
breathing
Activated with
increased ventilation to
cause contraction of
expiratory muscles
Brain Control Of Respiration
The Pons
– Pneumotaxic Center
Sends inhibitory signals to
inspiratory area in medulla
Shortens and quickens
breathing
Prevents over inflation of
lungs
– Apneustic Center
Continuously stimulates
the inspiratory area in
medulla
Prolongs inspiration
Deep and slow breathing
pneumotaxic
center
apneustic
center
Factors Influencing Ventilation
The Hering-Breuer Reflex
– Stretch receptors in lungs
Cause inhibition of inspiratory and apneustic centers
Prevents over inflation or over deflation of lungs
Cortical Input
– From cerebrum allows some voluntary control of
breathing
Factors Influencing
Ventilation
Chemical Influences
– CO2, O2 and H+ ion
concentrations in body
fluids can affect
ventilation
– Chemoreceptors in the
aortic arch and carotid
bodies send input to
respiratory centers
carotid
body
aortic
body
Chemical Influences
CO2 and H+ Ions
– Changes picked up by chemosensitive areas in
medulla
– Excite respiratory center when increased 
increased ventilation  more CO2 eliminated from
blood  H+ levels drop
– Small changes in H+ levels in the CSF can
drastically effect the medulla
O2 Levels
– Drop detected by aortic and carotid bodies
– Causes increased ventilation
Chemical Influences
pH Levels
– As pH falls, picked up by peripheral
chemoreceptors
– Cause increase in ventilation
– Elimination of CO2
Other Influences
Exercise
– Causes increased
ventilation
– Not related to partial
pressures or shortage
of O2
– May be caused by
input from
proprioceptors or
cerebrum
Other Influences
Altitude Changes
– Higher altitudes =
lower partial
pressure of gases
– Ventilation
increases
– Oxygen released to
tissues more
readily
Respiratory Disorders
Atelectasis
– Partial or complete lung collapse
– Can be caused by:
Obstructed bronchus
Any injury affecting thoracic pressures
Pneumothorax
– Pleural cavity becomes filled with air or gas
– Causes lung collapse
Respiratory Disorders
IRDS (Infant Respiratory Distress Syndrome)
– Usually the result of insufficient surfactant
– Alveoli collapse
RESPIRATORY DISORDERS
SIDS (Sudden Infant Distress Syndrome)
– Infants stop breathing during sleep
– Most common cause of death in infants under
1 year
– Possible causes
Viral or bacterial infection
Allergic response?
Malfunction of respiratory centers
Respiratory Disorders
COPD (Chronic Obstructive Pulmonary
Disease)
– Collection of diseases that cause chronic
difficulty in breathing and cough
– Often includes chronic bronchitis and
emphhysema
RESPIRATORY DISORDERS
Lung Cancer
– 1/3 of deaths in U.S.
– 90% are smokers
– Low cure rate
Pleurisy
– Inflammation of the pleura
– Friction and stabbing pains with breathing
– Can be caused by decreased pleural fluid