gas exchange in fish

Question 1

what is the ventilation system like in cartilaginous fish?

Answer 1

less efficient than bony fish
no special mechanism to force water over gills
blood travels in parallel flow
e.g. sharks

Question 2

where is water and blood on flow graphs?

Answer 2

water at top (pointing DOWN)
blood at bottom

Question 3

what is parallel flow?

Answer 3

water and blood flow in same direction
at start deoxygenated blood meets oxygenated blood with steep conc gradient
half way across gill plate, % oxygen saturation of water and blood reaches equilibrium
bood leaving gill is 50% saturated

Question 4

what are gills like in bony fish?

Answer 4

made up of numerous folds
operculum (covering over gills)
good blood supply
thin layer of cells

Question 5

what is the structure of gills?

Answer 5

4 pairs of gills
each gill supported by bony gill arch
along each gill is a double row of gill lamellae/plates which are on gill filaments
contains gill rakers

Question 6

what is countercurrent flow?

Answer 6

water and blood flow in opposite directions
blood is always meeting water with slightly higher 02 saturation
diffusion gradient is maintained across whole gill plate
(blood leaves about 95% saturated)

Question 7

where are gills located?

Answer 7

gills located between mouth/buccal cavity and chamber at sides of their mouth (operculum)

Question 8

how do fish inhale?

Answer 8

mouth opens
operculum closes
floor of mouth cavity is lowered
volume of mouth cavity increases
pressure falls
water is pulled into mouth

Question 9

how do fish exhale?

Answer 9

mouth closes
floor of mouth cavity is raised
volume decreases
pressure increases
water flows across gills
operculum is forced open