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Biology
Sylvia S. Mader
Michael Windelspecht
Chapter 35
Respiratory Systems
Lecture Outline
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Outline
• 35.1 Gas Exchange Surfaces
• 35.2 Breathing and Transport of Gases
• 35.3 Respiration and Human Health
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35.1 Gas Exchange Surfaces
• Respiration results in gas exchange
between the body’s cells and the
environment
– In terrestrial vertebrates, respiration includes:
• Ventilation (i.e., breathing)
• External respiration - gas exchange between the
air and the blood within the lungs
• Internal respiration - gas exchange between the
blood and the tissue fluid
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Respiration
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External Respiration
lungs
CO2
O2
CO2
O2
tissue cells
Internal Respiration
4
Gas Exchange Surfaces
• Gas exchange takes place by diffusion
• For external respiration to be effective, gasexchange regions must be:
– Moist
– Thin
– Large in relation to body size
• Effectiveness of diffusion is enhanced by
vascularization
• Delivery to cells is promoted by respiratory
pigments (e.g., hemoglobin)
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Gas Exchange Surfaces
• Overview of Gas-Exchange Surfaces
– Gases of air can dissolve in water
– However,
• When saturated, water contains a small fraction of
the O2 in same volume of air
• Water is much more dense than air
• Aquatic animals expend more energy to breathe
than do terrestrial animals
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Gas Exchange Surfaces
• Hydras and planarians
– Small animals with a large surface area
– Most of their cells exchange gases directly with the
environment
• Larger aquatic animals
– Often have gills
• Finely divided vascularized outgrowths of the body surface or
pharynx
• Gills of bony fishes
– Outward extensions of pharynx
– Ventilation is brought about by combined action of the
mouth and gill covers (opercula)
– Utilize a countercurrent exchange system to transfer
oxygen from the environment to their blood
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Hydra
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water flow
CO2
CO2
O2
O2
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Earthworm
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dorsal
blood
vessel
ventral
blood
vessel
CO2
O2
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Respiratory Organs
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gill
CO2
O2
gill filament
capillaries
blood vessels
trachea
a.
mammalian
lung
tracheoles
CO2
spiracles
trachea
CO2
O2
O2
alveoli
O2
CO2
c.
O2
CO2
spiracle
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b.
Anatomy of Gills in Bony Fishes
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operculum
lamellae
900X
a.
Water passes out of the pharynx
and over the finely divided gills.
Water passes by the gill lamellae in
a direction opposite to blood flow.
Oxygen content of water is
always higher than the oxygen
content of the blood.
O2-rich blood
Direction of H2O flow
O2-poor blood
lamellae
Direction of
H2O flow
O2 movement
blood
flow
water
flow
15%
blood
flow
gill arch
lamella
gill
filaments
b.
gill filament
c.
d.
(fish): © Dr. Jeffrey Isaacson, NebraskaWesleyan University; (gills): © David M. Phillips/Photo Researchers, Inc.
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Gas Exchange Surfaces
• Insects and other terrestrial arthropods
– A respiratory system consisting of branched
tracheae
– Oxygen enters tracheae at spiracles
– Tracheae branch until they end in tracheoles
that are in direct contact with body cells
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Tracheae of Insects
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air sac
tracheole
tracheae
spiracle
spiracle
air sacs
© Ed Reschke
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Gas Exchange Surfaces
• Terrestrial vertebrates have evolved lungs
– Vascular outgrowths from lower pharyngeal region
– Lungs of birds and mammals are elaborately
subdivided
• All terrestrial vertebrates, except birds, use a
ventilation mechanism whereby air moves in and
out by the same route
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Gas Exchange Surfaces
• Lungs of Humans
– As air moves through upper respiratory
system
– It is filtered to free it of debris
• Warmed
• Humidified
– When air reaches lungs
• It is at body temperature, and
• It is saturated with water
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Gas Exchange Surfaces
• Lungs of Humans
• Air passes from pharynx through the glottis
• Larynx and trachea
– Permanently held open by cartilage rings
– Facilitates movement of air
• When food is swallowed
– The larynx rises
– The glottis is closed by the epiglottis
– Backward movement of soft palate covers the entrance of
nasal passages into the pharynx
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Gas Exchange Surfaces
• Lungs of Humans (continued)
– Trachea divides
• Forms two primary bronchi
• Bronchi enter the right and left lungs
– Bronchi branch until there are a great number
of tiny bronchioles
• Each bronchiole terminates in an elongated space
enclosed by alveoli
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The Human Respiratory Tract
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cilia
goblet cell
epithelial
cell
blood flow
blood flow
particle
movement
nasal cavity
pulmonary arteriole
nostril
pulmonary
venule
mucus
pharynx
bronchiole
epiglottis
air
glottis
larynx
tracheal
lumen
trachea
bronchus
b. Tracheal lining
lobule
bronchiole
lung
capillary
network
diaphragm
alveoli
a. The path of air
c. Bronchiole and alveoli
b: © Ed Reschke
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35.2 Breathing and Transport of
Gases
• Breathing
– Inspiration in mammals
•
•
•
•
Creation of negative pressure in lungs
The rib cage is elevated
The diaphragm contracts and lowers
Thoracic pressure decreases to less than
atmospheric pressure
• Atmospheric pressure forces air into the lungs
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Breathing and Transport of
Gases
• Breathing
– Expiration in mammals
•
•
•
•
Creation of positive pressure in lungs
The rib cage is lowered
The diaphragm rises
Thoracic pressure increases to more than
atmospheric pressure
• Forces air out the lungs
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Inspiration
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trachea
intercostal
muscles
Rib cage
moves
up and out.
lungs
Diaphragm contracts
and moves down.
air in
lung
rib cage
When
pressure
in lungs
decreases,
air comes
rushing in.
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Expiration
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Rib cage
moves
down and in.
Diaphragm relaxes
and moves up.
air out
When
pressure
in lungs
increases,
air is
pushed out.
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Breathing and Transport of
Gases
• Ventilation
– All terrestrial vertebrates, with the exception
of birds, utilize a tidal ventilation mechanism
for breathing
• Volume of thoracic cavity and lungs is increased by
muscle contractions that lower the diaphragm and
raise the ribs
– Create negative pressure in the thoracic cavity and
lungs, and then air flows into the lungs during inspiration
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Breathing and Transport of
Gases
• Ventilation (continued)
– Birds use a one-way ventilation mechanism in
lungs
• Fresh air never mixes with used air
• Increases gas-exchange efficiency
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Respiratory System in Birds
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inhalation
lung
trachea
exhalation
lung
anterior
air sacs
posterior
air sacs
trachea
lung
1
Inhalation: Air enters posterior
air sacs.
anterior
air sacs
2
Exhalation begins: Air enters lung.
inhaled air
exhaled air
anterior
air sacs
exhalation
posterior
air sacs
4
Exhalation ends: Air exits anterior
air sacs.
3
Exhalation continues: Air enters
anterior air sacs.
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Breathing and Transport of
Gases
• Modifications of Breathing in Humans
• Normally, adults have a breathing rate of 12 to
20 ventilations per minute
• The rhythm of ventilation is controlled by a
respiratory center in the medulla oblongata
of the brain
– Sends out impulses to the diaphragm and
intercostal muscles of the rib cage so that
inspiration occurs
– When the respiratory center stops sending
neuronal signals to the diaphragm and the rib
cage, expiration occurs
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Nervous Control of Breathing
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brain
respiratory center:
automatically regulates
breathing
intercostal nerves:
stimulate the intercostal
muscles
intercostal muscles
phrenic nerve:
stimulates the diaphragm
diaphragm
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Breathing and Transport of
Gases
• Gas Exchange and Transport
• Partial pressure
• The amount of pressure exerted by a gas
• Gases diffuse from areas of higher to lower partial pressure
• Ventilation causes the alveoli to have a higher partial
pressure of oxygen and a lower partial pressure of
carbon dioxide than the blood in the pulmonary
capillaries
• This accounts for the exchange of gases in the lungs
• The opposite occurs in the tissues of the body
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Breathing and Transport of
Gases
• Transport of Oxygen and Carbon Dioxide
• External Respiration
• Most oxygen entering the pulmonary capillaries from the
alveoli combine with hemoglobin in red blood cells to form
oxyhemoglobin
• Internal Respiration
• Oxyhemoglobin gives up oxygen, which diffuses out of the
blood into the tissues where it is taken up by cells
• A small amount of carbon dioxide enters the blood from the
tissues and binds with hemoglobin to form
carbaminohemoglobin
• Most of the carbon dioxide is transported in the form of
bicarbonate ion
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Hemoglobin
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heme group
iron atom
beta chain
alpha chain
© Andrew Syred/Photo Researchers, Inc.
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External and Internal Respiration
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alveolus
HCO3-
plasma
pulmonary
capillary
External respiration
H+ + HCO3HbH+
CO2
RBC
H2 CO3
HbO2
H2O
CO2
RBC
HbCO2
pulmonary
capillary
O2
O2
alveolus
CO2
CO2 exits blood
plasma
O2
O2 enters blood
lung
pulmonary artery
pulmonary vein
heart
systemic vein
tissue cells
systemic artery
HCO3plasma
plasma
H+ + HCO3H2CO3
RBC
systemic
capillary
systemic
capillary
RBC
HbH+
CO2
H2O
HbCO2
O2
Internal respiration
tissue
fluid
CO2 enters blood
CO2
tissue
cell
tissue
cell
tissue
fluid
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O2 exits blood
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35.3 Respiration and Human
Health
• Disorders of the Upper Respiratory Tract
– Cold
• Mild viral infections
• Characterized by sneezing, runny nose, mild fever
• Antibiotics are ineffective for treatment
– Strep Throat
• Acute pharyngitis caused by a bacterium
(Streptococcus pyogenes)
• Severe sore throat, high fever, swollen tonsils
• Curable with antibiotics
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Respiration and Human Health
• Disorders of the Lower Respiratory Tract
– Trachea and Bronchi
• Choking
• Acute bronchitis
– Infection of primary and secondary bronchi
• Chronic bronchitis
– Airways become inflamed and filled with mucus
• Asthma
– Airways are unusually sensitive to specific irritants
» When exposed to these irritants, smooth muscles in
the bronchioles undergo spasms
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Respiration and Human Health
• Disorders Affecting the Lungs
– Pneumonia
• Viral, bacterial, or fungal infection of the lungs in
which bronchi and alveoli fill with fluid
– Pulmonary tuberculosis
• Caused by Mycobacterium tuberculosis
• Results in lung damage and reduced function
– Pulmonary fibrosis
• Fibrous connective tissue builds up in the lungs
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Respiration and Human Health
• Disorders Affecting the Lungs
– Emphysema
• Alveoli are distended and walls are damaged,
reducing the surface area available for gas
exchange
– Lung Cancer
• Begins with thickening and callusing of the cells
lining the airways
• Atypical cells appear in the thickened lining
• Cells from the tumor break loose and metastasize
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Respiration and Human Health
• Disorders Affecting the Lungs
– Cystic fibrosis (CF)
• Defective gene results in accumulation of mucus
secretions in the lungs
– Secretions become sticky and form plugs that
interfere with breathing
• Treatment involves clearing mucus from airways
administering mucus-thinning drugs and vigorously
slapping the patient on the back
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Common Bronchial and Pulmonary
Diseases
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asbestos
body
mucus
a. Acute Bronchitis
Airways are inflamed
due to infection or due
to an irritant. Coughing
brings up mucus and pus.
f. Pulmonary Fibrosis
Fibrous connective tissue
builds up in lungs, reducing
their elasticity.
tubercle
b. Asthma
Airways are inflamed due
to irritation, and bronchioles
constrict due to muscle spasms.
c. Pneumonia
Alveoli fill with pus and fluid,
making gas exchange difficult.
d. Pulmonary Tuberculosis
tubercles encapsulate
bacteria, and elasticity of
lungs is reduced.
e. Emphysema
Alveoli burst and fuse into
enlarged air spaces. Surface area
for gas exchange is reduced. 39
Smoking and Lung Disorders
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tumor
a. Normal lungs
b. Emphysema
c. Lung cancer
a: © Matt Meadows/Peter Arnold, Inc.; b: © SIU/Visuals Unlimited; c: © Biophoto Associates/Photo Researchers, Inc.
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