Transcript The Respiratory System - Cal State LA

BIOL 100C:
Introductory Biology III
The Respiratory System
Dr. P. Narguizian
Fall 2012
Principles of Biology
Education-Portal: Online Video
• Gas Exchange in the Human Respiratory System
http://education-portal.com/academy/lesson/gasexchange-in-the-human-respiratory-system.html
MECHANISMS
OF GAS EXCHANGE
Copyright © 2009 Pearson Education, Inc.
Overview: Gas exchange in an animal with lungs
involves breathing, transport of gases, and
exchange of gases with tissue cells
 Three phases of gas exchange
– Breathing
– Transport of oxygen and carbon dioxide in blood
– Body tissues take up oxygen and release carbon
dioxide
 Cellular respiration requires a continuous supply of
oxygen and the disposal of carbon dioxide
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• The three phases of gas exchange.
O2
1
Breathing
CO2
Lung
Circulatory
system
2
Transport
of gases by
the circulatory
system
Mitochondria
3
Exchange
of gases
with
body
cells
O2
CO2
Capillary
Cell
Animals exchange O2 and CO2 across moist body
surfaces
 Respiratory surfaces must be thin and moist for
diffusion of O2 and CO2
 Earthworms and other animals use their skin for gas
exchange
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• The entire outer skin of an earthworm serves as its
respiratory surface.
Cut
Cross section
of respiratory
surface (the
outer skin)
CO2
O2
Capillaries
Animals exchange O2 and CO2 across moist body
surfaces
 Most animals have specialized body parts that
promote gas exchange
– Gills in fish and amphibians
– Tracheal systems in arthropods
– Lungs in tetrapods that live on land
– Amphibians
– Reptiles
– Birds
– Mammals
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Body surface
Respiratory
surface
(gill)
CO2
O2
Capillary
• Gills are extensions of
the body surface that
function in gas
exchange with the
surrounding water.
• The tracheal system of an insect consists of tubes that extend
throughout the body.
Body surface
Respiratory
surface
(air tubes)
O2
CO2
Body cells
(no capillaries)
• Lungs are internal thin-walled sacs.
Body surface
CO2
CO2
O2
Respiratory
surface
(within lung)
O2
Capillary
Gills are adapted for gas exchange in aquatic
environments
 Gills
– Are extensions of the body
– Increase the surface to volume ratio
– Increase the surface area for gas exchange
– Oxygen absorbed
– Carbon dioxide released
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Gills are adapted for gas exchange in aquatic
environments
 In a fish, gas exchange is enhanced by
– Ventilation of the gills (moving water past the gills)
– Countercurrent flow of water and blood
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Gills are adapted for gas exchange in aquatic
environments
 Cold water holds more oxygen than warm water
 Fresh water holds more oxygen than salt water
 Turbulent water holds more oxygen than still water
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Gill
arch
Oxygen-poor
blood
Lamella
Oxygen-rich
blood
Direction
of water
flow
Gill
arch
Blood
vessels
Operculum
(gill cover)
Water flow
between
lamellae
Gill
filaments
Blood flow
through
capillaries
in lamella
Countercurrent exchange
Water flow, showing % O2
Diffusion
of O2 from
water to
blood
100 70
40
15
80
30
5
60
Blood flow in
simplified capillary,
showing % O2
The tracheal system of insects provides direct
exchange between the air and body cells
 Compared to water, using air to breathe has two
big advantages
– Air contains higher concentrations of O2
– Air is lighter and easier to move
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The tracheal system of insects provides direct
exchange between the air and body cells
 Air-breathing animals lose water through their
respiratory surfaces
 Insect tracheal systems use tiny branching tubes
– This reduces water loss
– Air is piped directly to cells
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• The tracheal system of an insect.
Air sacs
Tracheae
Opening
for air
Body
cell
Tracheole
Air
sac
Trachea
O2
CO2 Body wall
EVOLUTION CONNECTION: The evolution of
lungs facilitated the movement of tetrapods
onto land
 Tetrapods seem to have evolved in shallow water
– Fossil fish with legs had lungs and gills
– Legs may have helped them lift up to gulp air
– The fossil fish Tiktaalik illustrates these air-breathing
adaptations
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EVOLUTION CONNECTION: The evolution of
lungs facilitated the movement of tetrapods
onto land
 The first tetrapods on land diverged into three
major lineages
– Amphibians use small lungs and their body surfaces
– Nonbird reptiles have lower metabolic rates and
simpler lungs
– Birds and mammals have higher metabolic rates and
more complex lungs
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In the human respiratory system, branching tubes
convey air to lungs located in the chest cavity
 In mammals, air is inhaled through the nostrils
into the nasal cavity
– Air is filtered by hairs and mucus surfaces
– Air is warmed and moisturized
– Air is sampled for odors
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In the human respiratory system, branching tubes
convey air to lungs located in the chest cavity
 From the nasal cavity, air next passes
– To the pharynx
– Then larynx, past the vocal cords
– Into the trachea, held open by cartilage rings
– Into the paired bronchi
– Into bronchioles
– And finally to the alveoli, grapelike clusters of air
sacs, where gas exchange occurs
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• The anatomy of the
human respiratory
system.
Nasal
cavity
Pharynx
(Esophagus)
Larynx
Trachea
Left lung
Right lung
Bronchus
Bronchiole
Diaphragm
(Heart)
• Details of the structure of alveoli (right).
Oxygen-rich
blood
Oxygen-poor
blood
Bronchiole
Alveoli
Blood
capillaries
In the human respiratory system, branching tubes
convey air to lungs located in the chest cavity
 Alveoli are well adapted for gas exchange
– High surface area of capillaries
– High surface area of alveoli
 In alveoli
– O2 diffuses into the blood
– CO2 diffuses out of the blood
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• Scanning electron micrographs of the air spaces in
alveoli (left) and the capillaries that envelop the alveoli
(right).
Negative pressure breathing ventilates our lungs
 Breathing is the alternate inhalation and exhalation
of air (ventilation)
 Inhalation occurs when
– The rib cage expands
– The diaphragm moves downward
– The pressure around the lungs decreases
– And air is drawn into the respiratory tract
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Negative pressure breathing ventilates our lungs
 Exhalation occurs when
– The rib cage contracts
– The diaphragm moves upward
– The pressure around the lungs increases
– And air is forced out of the respiratory tract
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Rib cage gets
Rib cage
expands as
rib muscles
contract
Air
inhaled
smaller as
rib muscles
relax
Air
exhaled
Lung
Diaphragm
Diaphragm contracts
(moves down)
Diaphragm relaxes
(moves up)
Inhalation
Exhalation
Negative pressure breathing ventilates our lungs
 Not all air is expelled during exhalation
– Some air still remains in the trachea, bronchi,
bronchioles, and alveoli
– This remaining air is “dead air”
– Thus, inhalation mixes fresh air with dead air
 One-way flow of air in birds reduces dead air and
increases their ability to obtain oxygen
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Breathing is automatically controlled
 Breathing is usually under automatic control
 Breathing control centers in the brain sense and
respond to CO2 levels in the blood
 A drop in blood pH increases the rate and depth of
breathing
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• Control centers that regulate breathing respond
to the pH of blood and nervous stimulation from
sensors that detect CO2 and O2 levels.
Cerebrospinal
fluid
Brain
Pons
2 Breathing control
1 Nerve signals
trigger contraction
of muscles
Medulla
centers respond
to pH of blood
3 Nerve signals
indicating CO2
and O2 levels
CO2 and O2
sensors in aorta
Diaphragm
Rib muscles
TRANSPORT OF GASES
IN THE HUMAN BODY
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Blood transports respiratory gases
 The heart pumps blood to two regions
– The right side pumps oxygen-poor blood to the lungs
– The left side pumps oxygen-rich blood to the body
 In the lungs, blood picks up O2 and drops off CO2
 In the body tissues, blood drops off O2 and picks up
CO2
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Blood transports respiratory gases
 Gases move from areas of higher concentration to
areas of lower concentration
– Gases in the alveoli of the lungs have more O2 and less
CO2 than gases the blood
– O2 moves from the alveoli of the lungs into the blood
– CO2 moves from the blood into the alveoli of the lungs
– The tissues have more CO2 and less O2 than in the
blood
– CO2 moves from the tissues into the blood
– O2 moves from the blood into the tissues
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Inhaled air
• Gas transport and exchange in the body.
Exhaled air
Alveolar
epithelial
cells
Air spaces
CO2
O2
Alveolar
capillaries
CO2-rich,
O2-poor
blood
O2-rich,
CO2-poor
blood
Heart
Tissue
capillaries
CO2
Tissue cells
throughout
body
O2
Interstitial
fluid
Hemoglobin carries O2, helps transport CO2, and
buffers the blood
 Most animals transport O2 bound to proteins called
respiratory pigments
– Copper-containing pigment is used by
– Molluscs
– Arthropods
– Iron-containing hemoglobin
– Is used by almost all vertebrates and many invertebrates
– Transports oxygen, buffers blood, and transports CO2
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Hemoglobin loading and unloading of O2.
Iron atom
O2 loaded
in lungs
O2 unloaded
in tissues
Heme group
Polypeptide chain
O2
O2
Hemoglobin carries O2, helps transport CO2, and
buffers the blood
 Most CO2 in the blood is transported as bicarbonate
ions in the plasma
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Gas exchange
requires
moist, thin
often
relies on
(b)
(a)
for exchange of
O2
to transport
gases between
red blood
cells contain
CO2
(c)
(d)
needed
waste
for
product of
mammals
ventilate by
(e)
binds and
transports
and
helps
to
(f)
tissue cells
regulated by
breathing control
centers
transport CO2 and
buffer the blood
(g)
a.
b.
c.
d.
e.
f.
g.
h.
100
Llama
80
Human
60
40
20
0
0
20
40
60
PO (mm Hg)
2
80
100
You should now be able to
1. Describe the three main phases of gas exchange
in a human
2. Describe four types of respiratory surfaces and
the types of animals that use them
3. Explain how breathing air compares to using
water for gas exchange
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You should now be able to
4. Describe the parts and functions of the human
respiratory system
5. Explain how blood transports gases between the
lungs and tissues of the body
6. Describe the functions of hemoglobin
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