Transcript Gas Exchange

Respiratory System - A Quick Tour
• General Function
• Aquatic systems
• Land systems
• Insect
• Amphibian
• Mammalian
•
Introduction - the
search for
SA
(gas
exchange)
•
Size of respiratory surface area is a function of
organism’s metabolic needs....though all are
1. thin and have large surface areas.
2. Must remain moist (advantages/disadvantages)..
3. Who has larger SA to body mass ratio? ENDO or
ECTOtherms??
Gills are respiratory adaptation of most
aquatic animals
• Gills are outfoldings of the body surface that are
suspended in water.
• The total surface area of gills is often much greater than
that of the rest of the body.
• Many variations.
• Many segmented worms
have flaplike gills.
• The gills of clams,
crayfish, and many
other animals are
restricted to a local
body region (more like us).
Fig. 42.19
Gill Flavors..
The good and the bad..
• Water has both advantages and disadvantages as a
respiratory medium.
• ADVANTAGE
• moist.
• DISADVANTAGE
• Low gas concentration, heavy .
• Thus, gills must be very effective to obtain enough
oxygen (surface area exaggerated or metabolic rate
suffers).
Fig. 42.20
• This flow pattern is
countercurrent exchange
.
Essay stuff
ESSAY (BE ABLE TO
EXPLAIN THIS)
• Explain this
• Other examples
• Lacteal
• Thermoregulation
• All along the gill
capillary, there is a
diffusion gradient
• What would happen the
other way?
Fig. 42.20
Terrestrial animals  LUNGS
ADVANTAGES
• As a respiratory medium, air has many advantages
over water.
• What are they?
• ventilation requires less energy…:)
• Note; recent geologic findings indicate higher 02
concentrations 150-50 million years bp!!!!
• Who would have benefited?
Terrestrial animals LUNGS
DISADVANTAGES
• Air does have problems as a respiratory medium.
• What are they?
Really Small Land Animals..
• The tracheal system of insects is composed of air
tubes that branch throughout the body.
• The largest tubes, called tracheae, open to the outside,
and the finest branches extend to the surface of nearly
every cell. (A systemic system)
• The open circulatory system does not actively transport
oxygen and carbon dioxide.
• Explain WHY the tracheal system is well adapted to the
open circulatory system…
Fig. 42.22
Larger Land Animals:
Lungs
• Specialized Exchange
Surfaces…
•TISSUE??
•CELLS?
• lungs are restricted to one location….need for an
efficient “closed” circulatory system - see the connection?
• The respiratory surface of the lung is outside of body.
• Lungs have evolved in spiders, terrestrial snails, and
vertebrates.
• Among the vertebrates, amphibians have relatively
small lungs that do not provide a large surface
(many lack lungs altogether).
• Why are amphibians so susceptible to air quality??.
• Most reptiles and all birds and mammals rely
entirely on lungs for gas exchange.
• Turtles may supplement lung breathing with gas
exchange across moist epithelial surfaces in their mouth
and anus !?.
I think air goes the other way for us
Review and know gas pathway in lungs…
Fig. 42.23
• SURFACE AREA IN LUNGS
• At their tips, the tiniest bronchioles dead-end as a
cluster of air sacs called alveoli.
• Gas exchange occurs across the thin epithelium of the
lung’s millions of alveoli.
• These have a total surface area of about 100 m2 in
humans.
• Oxygen in the air entering the alveoli dissolves in the
moist film and rapidly diffuses across the epithelium
into a web of capillaries that surrounds each alveolus.
• Carbon dioxide diffuses in the opposite direction.
• HOW DO WE BREATH???
• The process of breathing, the alternate inhalation
and exhalation of air, ventilates lungs.
• A frog ventilates its lungs by positive pressure
breathing (the big bubble)
• Muscle activity forces air into lungs.
• Note – air force pilots are taught to do this in
emergency situations – valsalva maneuver
• mammals ventilate their lungs by negative
pressure breathing.
• This works like a suction pump, pulling air instead of
pushing it into the lungs.
• Muscle action changes the volume of the rib cage and the
chest cavity,
and the lungs
follow suit.
Fig. 42.24
• The lungs are enclosed by a double-walled sac
(pleura), A thin space filled with fluid separates
the two layers.
• Because of surface tension, the two layers behave like
two sheets of saran wrap stuck together by the adhesion
and cohesion of a film of water.
• The layers can slide smoothly past each other, but they
cannot be pulled apart easily.
• Surface tension couples movements of the lungs to
movements of the rib cage.
BREATHING….
• Lung volume increases as a result of contraction
of the rib muscles and diaphragm, a sheet of
skeletal muscle that forms the bottom wall of the
chest cavity.
• Contraction of the rib muscles (internal and external
intercostal muscles) expands the rib cage by pulling
the ribs upward and the breastbone outward.
• At the same time, the diaphragm contracts and descends
like a piston.
• Because air flows from higher pressure to lower
pressure, air rushes into the respiratory system.
BREATHING….
• During exhalation, the rib muscles and diaphragm
relax.
• The lungs behave as an inflated, untied, freshly
liberated (released) balloon (well, they don’t actually
fly out of the chest).
• Due to “elastic recoil of lungs.
• Lost with emphysema
• This forces air up the breathing tubes and out through
the nostrils.
• The volume of air an animal inhales and exhales
with each breath is called tidal volume.
• It averages about 500 mL in resting humans.
• The maximum tidal volume during forced
breathing is the vital capacity, which is about 3.4
L and 4.8 L for college-age females and males.
• The lungs hold more air than the vital capacity, but
some air remains in the lungs, the residual volume,
because the alveoli do not completely collapse.
• PROBLEM WITH MAMALLIAN
RESPIRATION
• Same as the problem of the gastrovascular cavity
in digestion – one opening, two way transport.
• Ventilation is much more complex in birds than in
mammals (more efficient).
• Besides lungs, birds have eight or nine air sacs that do
not function directly in gas exchange, but act as bellows
that keep air flowing through the lungs - one way flow less mixing of old air (think of three chambered heart).
• Instead of alveoli, which are dead ends, the sites of gas exchange in bird
lungs are tiny channels called parabronchi, through which air flows in
one direction.
• Partly because of this efficiency advantage, birds perform much better
than mammals at high altitude. - why is this a good thing??
Fig. 42.25
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
Control centers in the brain regulate the
rate and depth of breathing
• Sure you can hold your breath..but do you really
have control??.
• Coordination of Respiration and Circulation
• Our breathing control centers are located in two
brain regions, the medulla oblongata and the pons.
• Aided by the control center in the pons, the medulla’s
center sets basic breathing rhythm, triggering
contraction of the diaphragm and rib muscles.
• A negative-feedback mechanism via stretch receptors
prevents our lungs from overexpanding by inhibiting
the breathing center in the medulla.
Where is
conscience
thought??
Fig. 42.26
• The medulla’s control center monitors the CO2
level of the blood
• Its main cues about CO2 concentration come from
slight changes in the pH
• How is pH related to CO2??
• Oxygen concentrations in the blood usually have little
effect of the breathing control centers.
• Realize….Deep, rapid breathing purges the blood of so
much CO2 – how does this cause hyperventilation??
Respiratory pigments transport gases
and help buffer the blood
Realize different approaches..
hemocyanin, found in the hemolymph of
arthropods and many mollusks, has copper (get
it?) as its oxygen-binding component, coloring
the blood bluish.
• Respiratory pigments
• Hemoglobin – most vertebrates.
• Hemoglobin consists of four
subunits, each with a cofactor
called a heme group that has
an iron atom at its center.
• Because iron actually binds to
O2, each hemoglobin molecule
can carry four molecules of O2.
• Wow, what’s the other
molecule??
• Remember; hemoglobin must bind oxygen
reversibly,.
• What would be the consequence if not ??
• Do any substances bind irreversibly?
• Cooperative oxygen binding and release is
evident in the dissociation curve for
hemoglobin.
• What part of curve represents lung conditions?.
• What part represents body conditions?
Fig. 42.28a
• BOHR SHIFT!!!
• As with all proteins,
hemoglobin’s
conformation is
sensitive to a variety
of factors.
• pH effect on
hemoglobin = Bohr
shift.
• Why is Bohr shift
important during
exercise??.
free response!!
• Given what you know (and appreciate) about
hemoglobin/oxygen binding, draw a graph
showing the dissociation curves of adult
hemoglobin, fetal hemoglobin, and myoglobin.
Your graph should be correctly labeled (X, Y
axis, Title). Explain how your graph indicates the
relationship of these three molecules as they
function to transport oxygen. Hand in at end of
hour!!! (really)
hemoglobin also transports
carbon
dioxide and assists in buffering blood
pH.
• About 7% of the CO
2
released by respiring
cells is transported in solution.
• Another 23% binds to amino groups of
hemoglobin.
•About 70% is transported as bicarbonate
ions.
• Carbon dioxide from respiring cells diffuses into
the blood plasma and then into red blood cells,
where some is converted to bicarbonate, assisted
by the enzyme carbonic anhydrase.
• Fastest enzyme in the body!!!
• At the lungs, the equilibrium shifts in favor of
conversion of bicarbonate to CO2.
H2O +CO2  H2CO3  HCO3- + H+
Fig. 42.29
Fig. 42.29, continued
Free Diving
• When an air-breathing animal swims underwater,
it..can’t breath
• Most humans can only hold their breath for ?
• Seals and cetaceans (whales) ??
Little fish are tasty
• An adaptation of these deep-divers, such as the Weddell
seal, is an ability to store large amounts of O2 in the
tissues.
• Compared to a human, a seal can store about twice as much O2
per kilogram of body weight, mostly in the blood and muscles.
• MYOGLOBIN
• About 36% of our total O2 is in our lungs and 51% in our blood.
• In contrast, the Weddell seal holds only about 5% of its O2 in its
small lungs and stockpiles 70% in the blood.
• What organ would be HUGE in the seal compared to us?
• What do you think a training adaptation is related to this?
• Adaptations of deep sea divers.
• First, the seal has about twice the volume of blood per
kilogram of body weight as a human.
• Second, the seal can store a large quantity of
oxygenated blood in its huge spleen, releasing this
blood after the dive begins.
• Third, diving mammals have a high concentration of an
oxygen-storing protein called myoglobin in their
muscles.
• This enables a Weddell seal to store about 25% of its
O2 in muscle, compared to only 13% in humans.
Questions
• What is a pneumothorax- why bad, how fix??
• What is pericarditis- why bad, how fix?