Download Gas Exchange

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http://micro.magnet.fsu.edu/primer/techniques/hoffmangallery/images/stentor.jpg
In Stentor, a narrow
elongate shape permits
faster diffusion.
Myonemes along body
wall allow shape
contraction to mix cell
contents.
Exterior circulation by
cilia helps move fresh
water for gas
exchange, nutrients
closer to body, for
exchange by diffusion.
Gas Exchange in Unicellular Organisms
Size matters: microorganisms use simple diffusion for gas
exchange
Altering
shape may
make
diffusion
uptake a
shorter,
faster path
diffusion
http://www.microscopy-uk.org.uk/mag/imagsmall/amoebafeeding3.jpg
©1996 Norton Presentation Maker, W. W. Norton & Company
Unicellular animals
use diffusion
Simple aquatic multicellular animals
exchange gas through skin with capillary
exchange with blood system…evaginated
..or invaginated
Air breathers use lungs or tracheal systems
Nudibranch Flabellina verrucosa
http://www.sciencephoto.com/image/108117/530wm/C0043905-Nudibranch-SPL.jpg
©1996 Norton Presentation Maker, W. W. Norton & Company
Argopecten gibbus the Calico scallop, a bivalve mollusc
Ciliated surfaces move water across gills for gas exchange
Mexican Axolotl Ambystoma mexicanum
See Fig. 45.4 pg 906
http://images.nationalgeographic.com/wpf/media-live/photos/000/007/cache/mexican-axolotl_780_600x450.jpg
Perca flavescens http://www.tnfish.org/PhotoGalleryFish_TWRA/FishPhotoGallery_TWRA/images/YellowPerchMeltonHillNegus_jpg.jpg
oxygenated
water
operculum
deoxygenated,
carbonated water
Muscular operation of operculum
system moves water into mouth, over
evaginated gills, and out from trailing
edge of operculum
See Fig. 45.5 pg 907
http://courses.washington.edu/chordate/453photos/gut_photos/aseptal_gills2.jpg
©1996 Norton Presentation Maker, W. W. Norton & Company
How do evaginated gills work?
filament
enlarged…
Gill filament shows counter-current exchange design:
blood
return
to heart
water and blood
flow in opposite
directions
blood
from
heart
©1996 Norton Presentation Maker, W. W. Norton & Company
See Fig. 45.5 pg 907
100
70
40
15
100 85 70 55
53
90
60
30
5
5 20 35 50
52
blood
blood
100
100
water
50
Percent O2 Saturation
Percent O2 Saturation
Counter-current is more efficient than concurrent exchange
water countercurrent
water concurrent
blood
0
Countercurrent flow maximizes:
• Oxygen removal from water
• Blood oxygen content
See Fig. 45.6 pg 907
water
50
0
blood
This efficient system is needed
because oxygen solubility is very
low in water (10 mg/L) compared to
in air (286 mg/L).
Vertebrates evolved an invaginated gas exchange system:
©1996 Norton Presentation Maker, W. W. Norton & Company
The alveolate lung
Notice in this sequence how exchange surface area increases!
exhaled air
vibrates cords
for voice
©1996 Norton Presentation Maker, W. W. Norton & Company
Tidal flow in “blind
pouch” exchange
system
warms, humidifes,
traps particles
closes
glottis for
swallowing
mucus,
cartilage ridges
particles
keep airway open cilia lift mucus with swallowed
particles upward
©1996 Norton Presentation Maker, W. W. Norton & Company
The human breathing system: the larger structures
The mammalian lung gas exchange fine structure: the alveolus
©1996 Norton Presentation Maker, W. W. Norton & Company
See Fig. 45.10 pg 910
How the alveolate lung works
inhalation
Notice this is not a
counter-current
mechanism and is
inefficient
compared to gills
exhalation
“Artificial
respiration” is
possible
because of this!
Terrestrial animals do
not need efficient
exchange because air
holds much oxygen
compared to water
©1996 Norton Presentation Maker, W. W. Norton & Company
The ventilation movement in vertebrates with lungs has two parts
lungs nearly empty
lungs nearly full
rib
muscles
lift
contracts to
drop floor
©1996 Norton Presentation Maker, W. W. Norton & Company
For many singers and public speakers, the first lesson is
re-learning how to breathe! See Fig. 45.11 pg 911