gas exchange in fish

Question 1

how does water move in and out of a fish and what kind of mechanism is this?

Answer 1

enters the mouth (buccal cavity) and moves into the gills within the opercular cavity before leaving via the opercular valve at the inside of the fish’s head

continuous ventilation system because water travels continually in the same direction

Question 2

what role does a ventilation mechanism play in gas exchange?

Answer 2

maintains conc gradient for a faster rate of diffusion

Question 3

why does a fish require a continuous ventilation mechanism rather than a tidal ventilation mechanism?

Answer 3

-much lower conc of oxygen in water (1%) than air (21%)

-continuous system means there is fresh water over the gills at all times so fish can constantly maintain a gradient for uptake of oxygen via diffusion

Question 4

what are the feather like structures on a gill called?

Answer 4

gill filaments

Question 5

what is the benefit of having gill filaments?

Answer 5

the many gill filaments increase surface area for a faster rate of diffusion

Question 6

why are two sets of gill filaments on a gill at right angles to each other?

Answer 6

slows water flow down and gives more time for diffusion

Question 7

what additional structures does each gill filament have?

Answer 7

gill lamellae

Question 8

why do gill lamellae lead to more efficient gas exchange?

Answer 8

increase surface area due to many lamellae on each filament and so faster rate of diffusion

Question 9

where does oxygen have to diffuse in a gill filament?

Answer 9

across the wall of the gill lamellae and into the blood

Question 10

how does the wall of the gill lamellae allow for a fast rate of diffusion?

Answer 10

thin (one cell thick) to decrease length of diffusion pathway

this wall is epithelial tissue

Question 11

what is there in every gill lamellae and what does this provide?

Answer 11

a capillary bed which provides a very good blood flow

Question 12

what can be said about the thickness of the capillary wall and why?

Answer 12

one cell thick to provide short diffusion pathway

tissue is called endothelial tissue

Question 13

what can be said about the shape of the endothelial cells that make up the capillary wall?

Answer 13

they are flattened (long and thin) to provide a short diffusion pathway so faster rate of diffusion of oxygen into blood

Question 14

why is good blood flow important in gill lamellae?

Answer 14

maintains concentration gradient

Question 15

what is meant by counter-current flow?

Answer 15

water and blood flow in opposite directions

Question 16

how is equilibrium never reached with CC flow?

Answer 16

conc of ocygen in water is always higher than blood (conc gradient maintained) along the whole distance of the lamellae

Question 17

what is the benefit of equilibrium never being reached?

Answer 17

diffusion of oyxgen is occurring along the whole length of the lamellae

Question 18

what is the advantage of counter current flow?

Answer 18

blood becomes more saturated with oxygen because diffusion occurs all the way along the lamellae

so MORE oxygen delivered to respiring cells and they have a higher rate of respiration