ventilation in fish Flashcards
What are bony fish?
fish that evolved a skeleton of bones eg, trout, tuna, salmon, cod
Why did bony fish need to evolve to have specialised gas exchange systems?
-large and active creates high oxygen demand but have low SA:volume ratio
-scaly surface doesn’t allow oxygen through
-less oxygen in water than in air
What is the operculum?
flap of tissue, slightly behind the head that covers the gills
Where are the gills located?
in the opercular cavity
What attaches to the girl arches?
hundreds of gill filaments
What extends off the gill filaments?
small lamellae
What is the role of the gill lamella?
where gas exchange occurs
Why can’t fish breathe out of water?
their gills have a reduced surface area so oxygen can’t diffuse in efficiently
When does water enter non bony fish?
when they swim forward
How does water enter bony fish?
water passes into mouth space/buccal cavity even when they aren’t swimming
4 stages of inspiration (mouth open)
-oral valve opens
-mouth cavity expands as floor of buccal cavity drops to increase volume
-water is taken in through the open mouth
-operculum closes and moves outwards to assist water intake
3 stages of expiration
-oral valve shuts
-operculum opens
-pressure of opercular cavity falls so floor of buccal cavity lifts upwards
-pressure of water increased so it flows over the gills and gas exchange occurs
-sides of opercular cavity squeezes inwards on water and force it out of the operculum
adaptations of gill lamella
-good blood supply
-short diffusion distance
-massive SA
Why is the counter current system useful?
it ensures there’s always a steep concentration gradient for oxygen, for efficient diffusion
How does oxygen rich/poor blood travel through gills?
-oxygen poor blood enters capillaries of gill lamellae and oxygen diffuses fromoxygen poor water
-the now oxygen rich blood passes out of the lamellae and leaves the gills
