7.4 Ventilation and gas exchange in other organisms

what are spiracles

small openings on insects along the thorax and abdomen

what are sphincters for

to open or close spiracles (reduce water loss)

what do spiracles branch into

tracheae

what lines the tracheae

spirals of chitin

why are the tracheae lined

to keep them open if they are bent or pressed

why does little gas exchange happen in the tracheae

chitin is relatively impermeable to gases

what does tracheae branch into

tracheoles

what’s the difference between tracheae and tracheoles

tracheoles are elongated cells with no chitin lining (freely permeable to gases)

what is the role of tracheal fluid

keep tracheae moist and trap dust

why would lactic acid build up in tissues

when oxygen demand builds up to expose more surface area for gas exchange

how does lactic acid expose more SA for gas exchange

water moves out of the tracheoles by osmosis

why would insects want to inc the level of gas exchange

when the insect has very high energy demands

what is the mechanical ventilation of the tracheal system

air actively pumped into system by muscular pumping movements of thorax/abdomen

what do the muscle pumping movements do to insect

change volume of body and pressure in tracheae and tracheoles, air drawn in or forced out as pressure changes

how do insects increase amount of air moved through gas exchange system

collapsible enlarged trachae/air sacs, act as air reservoirs

what is needed for successful gas exchange in fish

• large surface area

• good blood supply

• thin layers

what is the operculum for

to actively maintain a flow of water over the gills

how do gills have a large surface area

gill lamellae and gill filaments

how do gills maintain good blood supply

counter current flow

what is counter current flow

when blood and water flow in opposite directions

why would fish have counter current flow

concentration gradient is maintained all long the gill

how if a thin diffusion distance created

capillaries are close to the surface of the gills

how do fish keep a current of water flowing over gills all the time

open and closing the mouth

what happens when mouth of fish is opened

• inc volume of buccal cavity

• pressure drops

• water moves into cavity

• operculum shut, dec pressure in opercular cavity

what happens when floor of buccal cavity starts to move up

• inc pressure in opercular cavity

• water moves from buccal cavity over gills

what happens when fish closes mouth

• operculum opens

• inc pressure in opercular cavity, force water over gills and out of operculum