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MODULE 3 - exchange and transport
3.1 exchange surfaces
fish gaseous exchange
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Cards (7)
fish can extract as much as
80%
of available
oxygen
passing through it's gills
features of gills
large
surface area
short
diffusion distance
high
concentration gradient
gills
4
gill
arches
on either side of fish
supports the gills
lies between the
mouth
cavity and the
opercular
flaps
gill lamella
increase
surface
area
inspiration
floor of buccal cavity is
lowered
opercular valve
closed
water enters through
mouth
over the
gills
expiration
mouth
closes
buccal
cavity
raised
water is forced over
open
opercular valve
counter current exchange
blood
and water flow over the gill lamella in
opposite
direction
relatively
constant
rate of
diffusion
favour the diffusion of
oxygen
from
water
into
blood
all the way across the
lamellae
almost
all
oxygen
is
absorbed
parallel flow system:
blood
and
water
move in the
same
direction
only about
50
% of oxygen is absorbed
favours
diffusion
of oxygen into
blood
for only
part
of the gill lamellae