gas exchange in fish

Question 1

what is the buccal cavity

Answer 1

the mouth

Question 2

what is countercurrent flow

Answer 2

where two fluids flow in opposite directions

Question 3

what are filaments

Answer 3

slender branches of tissue that make up the gill. often called primary lamellae

Question 4

what are lamellae

Answer 4

sometimes called secondary lamellae. these are folds of the filament to increase surface area. also called gill plates

Question 5

what is the operculum

Answer 5

a bony flap that protects and covers the gills

Question 6

what is special about aquatic organism

Answer 6

they dont need to try and prevent water loss when getting oxygen from water

Question 7

why is different about water compared to air

Answer 7

water is 1000 times denser than air and is 100x more viscous with a much lower oxygen content.

Question 8

how does the respiratory sytem of a fish work

Answer 8

they move water in one direction (takes less energy)

Question 9

how do bony fish exchange gases

Answer 9

with the water in which they live

Question 10

what do fish have to absorb oxygen from the water and release carbon dioxide into the water

Answer 10

gills

Question 11

is the oxygen concentration lower in water or in the air

Answer 11

the water

Question 12

how many pairs of gills do bony fish have

Answer 12

5

Question 13

what are the gills covered by

Answer 13

the operculum

Question 14

what does each gill consist of

Answer 14

two rows of gill filaments (primary lamellae) attached to a bony arch

Question 15

what do the surfaces of the thin filaments fold into

Answer 15

many secondary lamellae (gill plates)

Question 16

what do the gill plates provide

Answer 16

a large surface area

Question 17

where do the blood capillaries carry deoxygenated blood

Answer 17

close to the surface of the secondary lamellae where exchange takes place

Question 18

how does the blood flow in a fish

Answer 18

blood flows along the gill arch and out the filaments to the secondary lamellae. the blood then flows through capillaries in the opposite direction to the flow of water over the lamellae

Question 19

what does a countercurrent flow do

Answer 19

absorbs the maximum amount of oxygen from the water. countercurrent exchange removes up to 80% of the oxygen in the water by maintaining a steep gradient

Question 20

how does a countercurrent flow system work in a fish

Answer 20

1) in countercurrent flow/exchange blood flows in the opposite direction to the flow of water.
2) this causes oxygen to diffuse down the oxygen concentration gradient from the water to the blood
3) this results in the oxygen concentration between the blood in the gills and the water being maintained across the entire legnth of the gill lamella
4) even when the concentration of oxygen in the water is low at the operculum cavity end of the lamella, blood has just entered the gill lamella, therefore is even lower in oxygen concentration
5) this means there is still a diffusion gradient allowing the diffusion of oxygen from the water into the blood

Question 21

what happens if there is parallel (concurrent) flow of blood and water

Answer 21

the concentration of oxygen in the water and in the blood will equalise, therefore no more exchange of oxygen would take place.

Question 22

what must the flow of water be like for countercurrent flow gas exchange

Answer 22

must be unidirectional and not tidal

Question 23

why do the cells of bony fish have a high demand

Answer 23

bony fish are active animals

Question 24

what does the scaly outer covering of bony fish not allow for

Answer 24

gas exchange.

Question 25

what have bony fish evolved

Answer 25

a ventilatory system adapted to take in oxygen from the water and get rid of carbon dioxide from the water

Question 26

in which direction does water flow over the gills

Answer 26

in one direction

Question 27

what are some adaptations of the gills

Answer 27

- large surface area for diffusion - good blood supply to maintain a steep concentration gradient for diffusion - thin layers so diffusing substances have short distances to travel

Question 28

what are the gills contained in and covered by

Answer 28

contained in a gill cavity and covered by a protective operculum which is active in maintaining a flow of water over the gills

Question 29

why must fish be able to maintain a continuous flow of water over the gills even when they aren't moving

Answer 29

to allow efficient gas exchange at all times

Question 30

why does gas exchange need to be efficient

Answer 30

water is a medium where diffusion is slower than in air

Question 31

what does the bony arch do

Answer 31

supports the structure of the gills

Question 32

what is the main site of gas exchange in fish

Answer 32

gill filaments with their rich blood supply and large surface area. they occur in large stacks (gill plates)

Question 33

what do the gills constantly need and why

Answer 33

a flow of water to keep the gills apart in order to expose the large surface area needed for gas exchange

Question 34

what does afferent mean

Answer 34

describes things like nerves, blood vessels and arteries that lead towards or bring things (like blood) to an organ such as the heart or brain

Question 35

what does efferent mean

Answer 35

used to describe parts that carry or lead away things from organs

Question 36

what does an efferent blood vessel do

Answer 36

carries the blood leaving the gills in the opposite direction to the incoming water maintaining a steep concentration gradient

Question 37

what happens when fish are swimming

Answer 37

they keep a current of water flowing over their gills by opening their mouth and operculum

Question 38

what happens when fish stop moving

Answer 38

the flow of water stops

Question 39

how can bony fish keep water flowing over the gills even when they aren't moving

Answer 39

- they have a buccal-operculum pump, drawing water into the buccal cavity - the buccal cavity can change volume - the floor of the mouth moves downwards - the mouth closes and the floor is raised again pushing water through the gills - movements of the operculum are coordinated with the movements of the buccal cavity. as water is pushed from the buccal cavity the operculum moves outwards - the reduces the pressure in the operculum cavity (the space under the operculum)

Question 40

describe the mechanism of ventilation in fish

Answer 40

1) mouth opens (operculum is closed) 2) buccal cavity is lowered 3) increases the volume and decreases the pressure of the buccal cavity compared to outside 4) water rushes into the mouth down a pressure gradient 5) opercular cavity expands 6) the buccal cavity floor is raised 7) the pressure inside the buccal cavity is now higher than in the opercular cavity 8) water moves from buccal cavity over the gills into the opercular cavity 9) the mouth is now closed and the operculum opens 10) the sides of the opercular cavity move inwards increasing the pressure 11) water rushes out of the fish through the operculum

Question 41

why do the tips of adjacent gill filaments overlap

Answer 41

to increase the resistance to the flow of water over the gill surfaces and slows down the movement of water. this gives more time for gaseous exchange to take place

Question 42

what does a countercurrent exchange system ensure

Answer 42

stepps concentrations gradients are maintained so more gaseous exchange takes place. water moveing over the gills and the blood in the gill filaments flow in opposite directions

Question 43

how much oxygen do bony fish remove from the water flowing over them

Answer 43

80%