PowerLecture:
Chapter 11
The Respiratory System
Learning Objectives



Understand how body processes generate
a need to acquire oxygen and dispose of
carbon dioxide.
Describe the gradients that the respiratory
gases follow in their routes into and out of
the body.
Understand how the human respiratory
system functions and how it works in
coordination with other systems of the body.
Learning Objectives (cont’d)


Explain the controls over the breathing
processes.
List some of the things that can go wrong
with the respiratory system and explain the
mechanisms through which the breakdown
in the system occurs.
Impacts/Issues
Down in Smoke
Down in Smoke
Smoking poses a threat to human health
and survival.




Cilia that line the respiratory
airways and normally sweep
away pollutants and microbes
are immobilized for hours.
Smoke kills white blood cells
that defend the respiratory tract.
Smoking puts the body at
increased risk for cancer, high blood pressure,
and elevated levels of “bad” cholesterol.
Down in Smoke

The respiratory system functions to bring
oxygen into, and carbon dioxide out of, the
body.
Fig. 11.14a, p. 206
How Would You Vote?
To conduct an instant in-class survey using a classroom response
system, access “JoinIn Clicker Content” from the PowerLecture main
menu.

As tobacco use by its citizens declines, should the
United States encourage international efforts to
reduce tobacco use?


a. Yes, tobacco use is costly both in terms of personal
health and societal financial burden. The United States
should encourage international efforts to reduce
tobacco use.
b. No, the United States should not encourage
international efforts to reduce tobacco use. Tobacco
use, though deleterious to health, is a personal choice
that individuals have a right to make on their own.
Section 1
The Respiratory System—
Built for Gas Exchange
The Respiratory System –
Built for Gas Exchange
Airways are pathways for oxygen and
carbon dioxide.



The respiratory system brings in oxygen that
each body cell requires and takes away carbon
dioxide that every cell generates.
Through the nasal cavities of the nose, air
enters and leaves the respiratory system; the
nasal cavities are separated by a septum of
cartilage and bone.
The Respiratory System –
Built for Gas Exchange
•
Hair and ciliated epithelium filter dust and particles
from the air.
•
•
Blood vessels warm the air and mucus moistens it.
The paranasal sinuses lie just above the cavities
and are linked to them by channels.
Figure 11.2
The Respiratory System –
Built for Gas Exchange

Air moves via this route: nasal cavities >>>
pharynx >>> larynx >>> vocal cords (the gap
between the cords is the glottis) >>> trachea
>>> bronchi (one bronchus goes to each lung).
•
•
The trachea leads from the larynx downward to
branch into two bronchi, which are lined with cilia and
mucus to trap bacteria and particles.
The vocal cords at the entrance of the larynx vibrate
when air passes through the glottis, allowing us to
make sounds; during swallowing, the glottis is closed
to prevent choking.
vocal cords
glottis (closed)
glottis
(open)
epiglottis
tongue’s base
© 2007 Thomson Higher Education
Fig. 11.3, p. 197
The Respiratory System –
Built for Gas Exchange
Lungs are elastic and provide a large
surface area for gas exchange.



Human lungs are a pair of organs housed in
the rib cage above the diaphragm; the two
lungs are separated by the heart.
Each lung is enclosed by a pair of thin
membranes called pleurae (singular: pleura);
the pleural membrane is folded in a manner that
forms a pleural sac leaving an intrapleural
space filled with a lubricating intrapleural fluid.
The Respiratory System –
Built for Gas Exchange

Inside the lungs, bronchi narrow to form
bronchioles ending in respiratory
bronchioles.
•
•
Tiny clustered sacs called alveoli (singular:
alveolus) bulge out from the walls of the respiratory
bronchioles.
Together the alveoli provide a tremendous surface
area for gaseous exchange, with the blood located in
the dense capillary network surrounding each
alveolar sac.
bronchiole
alveolar sac
(sectioned)
alveolar
sac
alveolar
duct
alveoli
pulmonary
capillary
Fig. 11.1bc, p. 196
Nasal Cavity
Oral Cavity (mouth)
Pharynx (throat)
Epiglottis
Larynx (voice box)
Pleural
Membrane
Trachea (windpipe)
Intercostal
Muscles
Lung (one of a pair)
Bronchial Tree
Diaphragm
bronchiole
alveolar duct
alveolar sac
(sectioned)
alveolar
sac
alveoli
pulmonary capillary
Fig. 11.1, p. 196
Section 2
Respiration = Gas
Exchange
Respiration = Gas Exchange


Respiration is the overall exchange of
inhaled oxygen from the outside air for
exhaled carbon dioxide waste.
This exchange occurs in the alveoli;
afterward, the cardiovascular system is
responsible for moving gases in the body.
O2
O2
CO2
CO2
Cellular respiration in mitochondria
Whole body respiration
In-text Fig., p. 198
food, water intake
oxygen intake
DIGESTIVE
SYSTEM
nutrients,
water,
salts
RESPIRATORY
SYSTEM
oxygen
elimination
of carbon
dioxide
carbon
dioxide
CARDIOVASCULAR
SYSTEM
URINARY
SYSTEM
water,
solutes
elimination
of food
residues
rapid transport
to and from all
living cells
elimination of
excess water,
salts, wastes
Fig. 11-4, p. 198
Section 3
The “Rules” of Gas
Exchange
The “Rules” of Gas Exchange
Respiratory systems rely on the diffusion of
gases down pressure gradients.


Air is 78% nitrogen, 21% oxygen, 0.04% carbon
dioxide, and 0.96% other gases.
•
•
Partial pressures for each gas in the atmosphere
can be calculated; for example, oxygen’s is 160 mm
Hg.
Oxygen and carbon dioxide diffuse down pressure
gradients from areas of high partial pressure to areas
of low partial pressure.
Total atmospheric pressure = 760 mm Hg
78% N2
Partial pressure of
N2 = 600 mm Hg
21% O2
Partial pressure of
O2 = 160 mm Hg
760 mm Hg
1% CO2, other gases
Fig. 11.5, p. 198
The “Rules” of Gas Exchange

Gases enter and leave the body by diffusing
across thin, moist respiratory surfaces of
epithelium; the speed and extent of diffusion
depends on the surface area present and on
the partial pressure gradient.
The “Rules” of Gas Exchange
When hemoglobin binds oxygen, it helps
maintain the pressure gradient.



Hemoglobin is the main transport protein.
Each protein binds four molecules of oxygen in
the lungs (high oxygen concentration) and
releases them in the tissues where oxygen is
low; by carrying oxygen away from the lungs,
the gradient is maintained.
The “Rules” of Gas Exchange
Gas exchange “rules”
change when oxygen is
scarce.


Hypoxia occurs when
tissues do not receive
enough oxygen; at high
altitudes the partial
pressure of oxygen is
lower than at sea level,
so that hyperventilation
may occur.
Figure 11.6a
The “Rules” of Gas Exchange

Underwater, divers must
breathe pressurized air
from tanks and avoid
nitrogen narcosis,
where nitrogen dissolves
into the body, including
the brain; divers must
also ascend to the
surface slowly to prevent
nitrogen bubbles in the
blood—the “bends” or
decompression
sickness.
Figure 11.6b
Section 4
Breathing—
Air In, Air Out
Breathing
When you breathe, air pressure gradients
reverse in a cycle.


The respiratory cycle is the continuous in/out
ventilation of the lungs and has two phases:
•
•
Inspiration (inhalation) draws breath into the
airways.
Expiration (exhalation) moves a breath out of
the airways.
Breathing

During the cycle, the volume of the chest cavity
increases, then decreases, and the pressure
gradients between the lungs and outside air
reverse.
•
•
This works because the air in the airways is the
same pressure as the outside atmosphere.
Pressure in the alveoli (intrapulmonary pressure)
is also the same as the outside air.
INWARD BULK
FLOW OF AIR
Inhalation
Diaphragm
contracts and
moves down. The
external
intercostal
muscles contract
and lift the rib
cage upward and
outward. The lung
volume expands.
OUTWARD BULK
FLOW OF AIR
Exhalation
Diaphragm and
external
intercostal
muscles return
to the resting
positions. Rib
cage moves
down. Lungs
recoil Fig.
passively.
11.7, p. 200
Breathing

The basic respiratory cycle.
•
•
•
To inhale, the diaphragm contracts and flattens,
muscles lift the rib cage upward and outward, the
chest cavity volume increases, internal pressure
decreases, air rushes in.
To exhale, the actions listed above are reversed; the
elastic lung tissue recoils passively and air flows out
of the lungs.
Active exhalation involves contraction of the
abdominal muscles to push the diaphragm upward,
forcing more air out.
Breathing

Another pressure gradient aids the process.
•
•
The lungs are stretched to fill the thoracic cavity by a
slight difference between the intrapulmonary
pressure (higher) and the intrapleural pressure
(lower).
In a collapsed lung (pneumothorax), air enters the
pleural cavity, disrupting the normal expansion and
contraction of the lungs.
Breathing
How much air is in a “breath”?


About 500 ml of air (tidal volume) enters and
leaves the lungs with each breath.
•
•
A human can forcibly inhale 3,100 ml of air
(inspiratory reserve volume) and forcibly exhale
1,200 ml (expiratory reserve volume).
The maximum volume that can be moved in and out
is called the vital capacity (4,800 ml for males,
3,800 ml for females).
6,000
Lung volume (milliliters)
5,000
4,000
inspiratory
reserve
volume
tidal
volume
vital
capacity
total lung
capacity
3,000
2,000
expiratory
reserve
volume
1,000
residual
volume
0
time
Fig. 11.8, p. 201
Breathing


A residual volume of about 1,200 ml remains
in the lungs and cannot be forced out.
Sometimes food enters the trachea rather than
the esophagus; it can be forced out by the
Heimlich maneuver, which forces the
diaphragm to elevate, pushing air into the
trachea to dislodge the obstruction.
a Place a fist just above the choking person’s navel,
with the flat of your thumb against the abdomen.
Fig. 11.9a, p. 201
b Cover the fist with your other hand. Thrust both fists up and
in with enough force to lift the person off his or her feet.
Fig. 11.9b, p. 201
Section 5
How Gases Are
Exchanged and
Transported
How Gases Are
Exchanged and Transported
Ventilation moves gases into and out of the
lungs; it is different from respiration, which
is the actual exchange of gases between
the blood and cells.



In external respiration, oxygen moves from
the alveoli to the blood; carbon dioxide moves
in the opposite direction.
In internal respiration, oxygen moves from the
blood into tissues and vice versa for carbon
dioxide.
How Gases Are
Exchanged and Transported
Alveoli are masters of gas exchange.


Each alveolus is only a single layer of epithelial
cells surrounded by a thin basement membrane
and a net of lung capillaries, also with thin
basement membranes.
•
•
•
Between the two basement membranes is a film of
fluid.
Together the system forms the respiratory
membrane.
The partial pressure gradients are sufficient to move
oxygen in and carbon dioxide out of the blood,
passively.
How Gases Are
Exchanged and Transported

Pulmonary surfactant is a secretion produced
by the alveoli that reduces the surface tension
of the film to prevent collapse of the alveoli;
infant respiratory distress syndrome occurs
in premature babies who lack the ability to
make the surfactant.
alveolar epithelium
respiratory membrane
capillary
endothelium
pore for
air flow
between
adjoining
alveoli
space
inside
alveolus
a Surface view of capillaries
associated with alveoli
b Cutaway view of one
alveolus, showing the
respiratory membrane
red
blood
cell
fusedtogether
basement
membranes
of both
epithelia
c Closer view of the
respiratory
membrane’s
structure
Fig. 11.10, p. 202
pore for air
flow between
adjoining
alveoli
a. Surface view of capillaries associated with alveoli
Fig. 11.10a, p. 202
pore for airflow
between adjoining alveoli
respiratory membrane
(see next slide)
space
inside
alveolus
red blood cell
b. Cutaway view of one alveolus,
showing the respiratory membrane
Fig. 11.10b, p. 202
alveolar epithelium
capillary endothelium
fused-together
basement membranes
of both epithelia
c. Closer view of the respiratory
membrane’s structure
Fig. 11.10c, p. 202
How Gases Are
Exchanged and Transported
Hemoglobin is the oxygen carrier.


Blood cannot carry sufficient oxygen and
carbon dioxide in dissolved form as the body
requires; hemoglobin helps enhance its
capacity to carry gases by transporting oxygen.
•
•
Oxygen diffuses down a pressure gradient into the
blood plasma >>> red blood cells >>> hemoglobin
where it binds at a ratio of four oxygens to one
hemoglobin to form oxyhemoglobin.
Hemoglobin gives up its oxygen in tissues where
partial pressure of oxygen is low, blood is warmer,
and pH is lower; all three conditions occur in tissues
with high metabolism.
O2 160
DRY
INHALED AIR CO2 0.3
O2 120
MOIST
CO2 27 EXHALED AIR
alveolar sacs
O2 104 CO2 40
pulmonary O2 40
arteries CO2 45
O2 100 pulmonary
veins
CO2 40
start of
systematic
capillaries
O2 100
CO2 40
start of
systematic
veins
O2 40
CO2 45
cells of body tissue
O2 less than 40
CO2 more than 45
© 2007 Thomson Higher Education
Fig. 11.11, p. 203
How Gases Are
Exchanged and Transported

When tissues are chronically low in oxygen, red
blood cells produce DPG (2,3diphosphoglycerate), which decreases the
affinity of hemoglobin for oxygen, allowing more
oxygen to be released to the tissues.
Hemoglobin and blood plasma carry carbon
dioxide.


Because carbon dioxide concentration is higher
in the body tissues rather than in blood, it
diffuses into the blood capillaries.
How Gases Are
Exchanged and Transported

•
Seven percent remains dissolved in plasma, 23%
binds with hemoglobin (forming
carbaminohemoglobin) and 70% is in bicarbonate
form.
•
Bicarbonate and carbonic acid formation is
enhanced by carbonic anhydrase, an enzyme
located in the red blood cells.
Reactions that make bicarbonate are reversed
in the alveoli where the partial pressure of
carbon dioxide is low.
Section 6
Homeostasis Depends
on Controls over
Breathing
Homeostasis Depends on
Controls Over Breathing
A respiratory pacemaker controls the
rhythm of breathing.


Automatic mechanisms ensure a regular cycle
of ventilation.
•
•
Clustered nerve cells in the medulla coordinate the
signals for the timing of exhalation and inhalation;
the pons fine tunes the rhythmic contractions.
The nerve cells are linked to the diaphragm muscles
and the muscles that move the rib cage; during
normal inhalation, nerve signals travel from the brain
to the muscles causing them to contract and allowing
the lungs to expand.
Homeostasis Depends on
Controls Over Breathing


Normal exhalation follows relaxation of muscles
and elastic recoil of the lungs.
When breathing is deep and rapid, stretch
receptors in the airways send signals to the
brain control centers, which respond by
inhibiting contraction of the diaphragm and rib
muscles, forcing you to exhale.
neurons
(pacemaker for
respiration)
brain stem
(pons and medulla)
vagus nerve
motor pathways via
spinal cord
phrenic nerve to diaphragm
intercostal nerves to
rib muscles
stretch receptors in
alveoli of lungs
diaphragm
© 2007 Thomson Higher Education
Fig. 11.12, p. 204
Homeostasis Depends on
Controls Over Breathing
CO2 is the trigger for controls over the rate
and depth of breathing.


The nervous system is more sensitive to levels
of carbon dioxide and uses this gas to regulate
the rate and depth of breathing.
•
•
Sensory receptors in the medulla detect hydrogen
ions produced when dissolved carbon dioxide leaves
the blood and enters the cerebrospinal fluid
bathing the medulla.
The drop in pH in the cerebrospinal fluid triggers
more rapid and deeper breathing to reduce the levels
of carbon dioxide in the blood.
Homeostasis Depends on
Controls Over Breathing

Changes in the levels of carbon dioxide,
oxygen, and blood pH are also detected by
carotid bodies, located near the carotid
arteries, and aortic bodies, located near the
aorta; both receptors signal increases in
ventilation rate to deliver more oxygen to
tissues.
brain-stem (pons and
medulla) receptors
detect decreases in
pH of cerebrospinal
fluid (due to rising
CO2 in blood)
carotid bodies
(CO2, O2
receptors)
aortic bodies
(O2 receptors)
heart
lungs
spinal cord
© 2007 Thomson Higher Education
Fig. 11.13, p. 205
Homeostasis Depends on
Controls Over Breathing
Chemical controls in alveoli help match air
flow to blood flow.



When the rate of blood flow in the lungs is
faster than the air flow, the bronchioles dilate to
enhance the air flow and thus the rate of
diffusion of the gases.
When the air flow is too great relative to the
blood flow, oxygen levels rise in the lungs and
cause the blood vessels to dilate, increasing
blood flow.
Homeostasis Depends on
Controls Over Breathing
Apnea is a condition in which breathing
controls malfunction.



Apnea is a brief interruption in the respiratory
cycle; breathing stops and then resumes
spontaneously.
Sleep apnea is a common problem of aging
because the mechanisms for sensing changing
oxygen and carbon dioxide levels gradually
become less effective over the years.
Section 7
Disorders of the
Respiratory System
Disorders of the Respiratory System
Tobacco is a major threat.




Smoking has both immediate effects (for
example, loss of cilia function) and long term
effects, such as lung cancer.
Even one cigarette can cause
you damage as well as hurt those
around you through secondhand
smoke.
A variety of pathogens can infect the
respiratory system.
Figure 11.17
Fig. 11.14b, p. 206
Disorders of the Respiratory System



Pneumonia occurs when inflammation in lung
tissue and the buildup of fluids makes breathing
difficult; pneumonia can sometimes occur when
infections that start in the nose and throat, such
as from influenza, spread.
Tuberculosis arises from infection by the
bacterium Mycobacterium tuberculosis; the
disease destroys patches of lung tissue and
can cause death if untreated.
Histoplasmosis is caused by a fungus;
treatment is possible, but the infection can
sometimes spread to the eyes, causing
impairment or blindness.
Disorders of the Respiratory System
Irritants cause other disorders.


Bronchitis, caused by air pollution, cigarette
smoke, or infection, leads to increased mucus
secretions, interference with ciliary action, and
eventual inflammation and possible scarring of
the bronchial walls.
Figure 11.18
Fig. 11.18a, p. 210
Disorders of the Respiratory System

If bronchitis progresses so that more of the
bronchi become scarred and blocked with
mucus, emphysema may result; here alveoli
also begin to break down, further eroding the
ability to breathe.
Fig. 11.15, p. 207
Disorders of the Respiratory System

Asthma occurs in response to various
allergens; smooth muscles in the bronchiole
walls contract in spasms, mucus rushes in, and
breathing becomes difficult. Steroid inhalers
may be needed to relieve symptoms.
Figure 11.16