7.4 Ventilation In Fish Flashcards
why do fish need a specialised exchange system
oxygen dissolves less readily in water as water is 100 times more viscous than
air and has a much lower O2 content
what is the structure of gills like
a series of gills on each side of the head each gills arch consists of two stacks of filaments and each filament has a row of lamallae this increase surface area
what’s the surface of the lamallae like
it’s surface is a single layer of squamous epithelium cells that cover a vast network of capillaries which gives a good blood supply
what exposes the large surface area of the filaments
the flow of water running between the filaments keeping them apart
what’s the main site of gas exchange in fish
the lamallae
what’s the counter current system
when the capillary system within the lamallae ensures that blood flow is in the opposite direction to the flow of water this ensures the concentration gradient is maintained for the whole length of the capillary
the water with the lowest oxygen content is found adjacent to the most deoxygenated blood
what does the ventilation mechanism in fish do
it constantly pushes water over the gills so they are always supplied with water rich in oxygen to maintain the concentration gradient
how does inspiration happen in fish
when they open their mouth the floor of the buccal cavity lowers so the volume inside the buccal cavity increase while the pressure lowers
now pressure is higher outside of fishes mouth so water flows into the buccal cavity, at the same time the opercular valve is shut and the opercular cavity which contains the gills expands this lowers the pressure in the opercular cavity so the flow of the buccal cavity moves back up and the water in there moves over the gills
how does expiration happen in fish
the mouth closes and the operculum opens up and the sides of the opercular cavity move inwards all of this increases the pressure in the opercular cavity and forces water over the gills and out of the operculum and the flow of the buccal cavity is steadily moved up maintaining a water flow over the gills
what’s the operculum
a flap of tissue covering the gills
what helps ensure effective gaseous exchange in fish
tips of adjacent gill filaments overlap increases resistance to the flow of water which slows down the movement and ensures the gas exchange has longer to take place
counter current system ensures steep conc gradient
