Respiratory System
1
Respiration
• Ventilation: Movement of air into & out of
lungs
• External respiration: Gas exchange b/n air
in lungs & blood
– Transport of O2 and CO2 in the blood
• Internal respiration: Gas exchange b/n the
blood & tissues
2
Respiratory System Functions
• Gas exchange: O2 enters blood & CO2 leaves
• Regulation of blood pH: Altered by changing
blood CO2 levels
• Voice production: Movement of air past vocal
folds makes sound & speech
• Olfaction: Smell occurs when airborne
molecules drawn into nasal cavity
• Protection: Against microorganisms by
preventing entry & removing them
3
Respiratory System Divisions
• Upper tract
– Nose, pharynx &
associated
structures
• Lower tract
– Larynx, trachea,
bronchi, lungs
4
Nose and Pharynx
• Nose
– External nose
– Nasal cavity
• Functions
– Passageway for air
– Cilia cleans the air
– Mucous humidifies
(moistens air inhaled)
– Capillaries warm air
– Smell
– Along with paranasal
sinuses are resonating
chambers for speech
• Pharynx
– Common opening for
digestive &
respiratory systems
– Three regions
• Nasopharynx
• Oropharynx
• Laryngopharynx
5
Larynx
• Functions
– Maintain an open passageway for air movement
– Epiglottis & vestibular folds prevent swallowed material from
moving into larynx (can move to cover trachea)
– Vocal folds are primary source of sound production
6
Structure of Larynx
– AKA voice box
– Thyroid cartilage: AKA
Adam’s apple
• Protects vocal cords
• Moves when you swallow
– Epiglottis: closes off
larynx so food & liquid
travel down the
esophagus
7
Voice Production
• False vocal cords:
assist w/ hold breath
• True vocal cords:
– Space between them
called glottis
– Vibration produces
sound
– In combination with
tongue, mouth, & nose
to produce words
8
Trachea
•
Windpipe
•
Divides to form
Insert Fig 23.5 all
but b
– C-shaped cartilage with
smooth muscle which keeps
diameter to allow fluent air
flow
– Lined with cilia and mucus
to moisten and clean air
– Primary bronchi
– Carina: Cough reflex
9
Organs of Respiration
• Trachea:
– AKA windpipe
– Smooth muscle
supported by C-shaped
rings of cartilage
• food can travel down
esophagus easier
– Passageway for air
from larynx to bronchi
– Lined w/ cilia & mucous
10
Tracheobronchial Tree
• Conducting zone
– Trachea to terminal bronchioles which is
ciliated for removal of debris
– Passageway for air movement
– Cartilage holds tube system open & smooth
muscle controls tube diameter
• Respiratory zone
– Respiratory bronchioles to alveoli
– Site for gas exchange
11
Organs of Respiration
• Bronchi:
– Left & right
primary bronchi
branch off
trachea
– Lined w/ cilia
– Supported by
cartilage
12
Bronchial Tree
Primary bronchi
Secondary bronchi
Tertiary bronchi
bronchioles
Terminal bronchioles
Respiratory bronchioles
Alveolar ducts
Alveolar sacs
alveoli
13
Terminal bronchiole: the last portion of the nonrespiratory conducting
airway, which subdivide into respiratory bronchioles.
Respiratory bronchiole: the final branch of a bronchiole, communicating
directly with the alveolar ducts; a subdivision of a terminal bronchiole,
it has alveolar outcroppings and itself divides into several alveolar
ducts.
14
Bronchioles and Alveoli
15
Alveolus and Respiratory
Membrane
16
Lungs
• Two lungs: Principal organs of respiration
– Right lung: Three lobes
– Left lung: Two lobes
17
Organs of Respiration
• Alveoli:
– Extremely thin-walled
sacs covered w/
capillaries
– CO2 & O2 move by
diffusion across the
respiratory membrane
– About 300 million
alveoli in two lungs
– Size of a tennis court
18
Organs of Respiration
• Alveoli:
– Surfactant lines the
alveoli to aid diffusion
& decrease surface
tension
– To prevent the alveoli
from collapsing &
sticking shut
19
Pleura
• Pleural fluid produced by pleural membranes
– Acts as lubricant
– Helps hold parietal & visceral pleural membranes
together
20
Ventilation
• Movement of air into and out of lungs
• Air moves from area of higher pressure to
area of lower pressure (AKA Diffusion)
• Pressure is inversely related to volume
21
Inspiration
• Breathing in
• When pressure in the
lungs is less than the
air pressure in the
atmosphere
• Diaphragm— will
contract and lower,
increasing the size of
the thoracic cage
22
Inspiration
• Increased volume will
decrease the
pressure & the lungs
will expand
23
Expiration
• Breathing out
• When the pressure
inside the lungs is
greater than the
pressure in the
atmosphere
• Diaphragm— relaxes
and rises; decreases
the size of the
thoracic cage
24
Expiration
• Decreased
volume will
increase pressure
& lungs will
decrease and
push air out
25
Internal Respiration
• Exchange of O2 and
CO2 between tissue
capillaries and tissue
cells
• CO2 moves from high
concentration in
cells to low
concentration in
blood
26
External Respiration
• Conversion of
deoxygenated blood
to oxygenated blood
– Aided by thin
membranes
– Large surface area
– Narrow capillaries
27
Changing Alveolar Volume
• Lung recoil
– Causes alveoli to collapse resulting from
• Elastic recoil and surface tension
– Surfactant: Reduces tendency of lungs to collapse
• Pleural pressure
– Negative pressure can cause alveoli to
expand
– Pneumothorax is an opening between
pleural cavity & air that causes a loss of
pleural pressure
28
Compliance
• Measure of the ease with which lungs &
thorax expand
– The greater the compliance, the easier it is
for a change in pressure to cause expansion
– A lower-than-normal compliance means the
lungs and thorax are harder to expand
• Conditions that decrease compliance
– Pulmonary fibrosis
– Pulmonary edema
– Respiratory distress syndrome
29
Pulmonary Volumes
• Tidal volume
– Volume of air inspired or expired during a normal
inspiration or expiration
• Inspiratory reserve volume
– Amount of air inspired forcefully after inspiration of
normal tidal volume
• Expiratory reserve volume
– Amount of air forcefully expired after expiration of
normal tidal volume
• Residual volume
– Volume of air remaining in respiratory passages and lungs
after the most forceful expiration
30
Pulmonary Capacities
• Inspiratory capacity
– Tidal volume plus inspiratory reserve volume
• Functional residual capacity
– Expiratory reserve volume plus the residual volume
• Vital capacity
– Sum of inspiratory reserve volume, tidal volume, and
expiratory reserve volume
• Total lung capacity
– Sum of inspiratory and expiratory reserve volumes
plus the tidal volume and residual volume
31
Spirometer and Lung
Volumes/Capacities
32
Minute and Alveolar
Ventilation
• Minute ventilation: Total amount of air
moved into & out of respiratory system per
minute
• Respiratory rate or frequency: Number of
breaths taken per minute
• Anatomic dead space: Part of respiratory
system where gas exchange does not take
place
• Alveolar ventilation: How much air per
minute enters the parts of the respiratory
system in which gas exchange takes place33
Physical Principles of Gas
Exchange
• Partial pressure
– The pressure exerted by each type of
gas in a mixture
• Diffusion of gases through liquids
– Concentration of a gas in a liquid is
determined by its partial pressure and
its solubility coefficient
34
Physical Principles of Gas
Exchange
• Diffusion of gases through the respiratory
membrane
– Depends on membrane’s thickness, the diffusion coefficient
of gas, surface areas of membrane, partial pressure of
gases in alveoli and blood
• Relationship between ventilation and
pulmonary capillary flow
– Increased ventilation or increased pulmonary capillary blood
flow increases gas exchange
– Physiologic shunt is deoxygenated blood returning from
lungs
35
Oxygen & Carbon Dioxide
Diffusion Gradients
• Oxygen
– Moves from alveoli
into blood. Blood is
almost completely
saturated with
oxygen when it leaves
the capillary
– C02 in blood
decreases because of
mixing with
deoxygenated blood
– Oxygen moves from
tissue capillaries into
the tissues
• Carbon dioxide
– Moves from tissues
into tissue
capillaries
– Moves from
pulmonary
capillaries into the
alveoli
36
Hemoglobin and Oxygen
Transport
• Oxygen is transported by hemoglobin
(98.5%) and is dissolved in plasma
(1.5%)
37
Transport of Carbon Dioxide
• Carbon dioxide is transported as
bicarbonate ions (70%) in combination
with blood proteins (23%) and in
solution with plasma (7%)
38
Herring-Breuer Reflex
• Limits the degree of inspiration and
prevents overinflation of the lungs
– Infants
• Reflex plays a role in regulating basic rhythm of
breathing and preventing overinflation of lungs
– Adults
• Reflex important only when tidal volume large as in
exercise
39
Ventilation in Exercise
• Ventilation increases abruptly
–
–
–
–
At onset of exercise
Movement of limbs has strong influence
Learned component
Decreases slightly
• Ventilation increases gradually
– After immediate increase, gradual
increase occurs (4-6 minutes)
– Anaerobic threshold is highest level of
exercise without causing significant
change in blood pH
• If exceeded, lactic acid produced by skeletal muscles
40
Disorders
• Asthma— spasms of smooth muscle in
the bronchioles
• Lung cancer
– Constant irritation produces excess
mucous and puts unnecessary stress on
the bronchi
– Alveoli destroyed by WBC’s acting on the
irritation
– Structural cells disappear and cancer
cells take over
41
Disorders
• Emphysema— alveolar walls lose their
elasticity
– Some alveoli merge and reduce volume
– Have to work voluntarily to exhale
• Bronchitis— inflammation of the bronchi
– Creates site for infection and increases
mucous
42
Disorders
• Pneumonia— infection or inflammation of
the alveoli
• Tuberculosis (TB)— bacterial infection
that destroys lung tissue and is replaced
by non-elastic connective tissue
43
Disorders
• Respiratory Distress Syndrome (RDS)
– Lack of surfactant makes breathing difficult
– Alveoli are sticking together
– Occurs in infants
• Pulmonary Embolism
– blood clot obstructs circulation to lung tissue
& tissue dies
44
Disorders
• Respiratory Failure
– Not enough O2 to maintain metabolism
– Cannot eliminate enough CO2
– Caused by:
•
•
•
•
Drugs
Stroke
CO poisoning
Shock
45
Disorders
• Colds and Flu— viral infections
• Sudden Infant Death Syndrome (SIDS)
–
–
–
–
Crib death
Occurs between 1 week and 12 months
Cause is unknown
Baby stops breathing
• Lung Caner:
http://today.msnbc.msn.com/id/26184891/v
p/36258056#36258056
46
Disorders
• Laryngitis— vocal cords
• Pharyngitis— sore throat
• Rhinitis— lining of the
nose
47
Effects of Aging
• Vital capacity and maximum minute
ventilation decrease
• Residual volume and dead space increase
• Ability to remove mucus from respiratory
passageways decreases
• Gas exchange across respiratory
membrane is reduced
48