ch7 - gas exchange and ventilation in insects

why do insects require a gas exchange system

exoskeleton is made from chitin which is very tough and prevents direct gas exchange from occurring through their skin

what is a benefit of the exoskeleton

outer layer of the exoskeleton is waxy cuticle layer which reduces water loss

what is the insect gas exchange system called

tracheal system

what structures does the tracheal system consist of

spiracles > tracheae > tracheoles > cells

what do each of these structures do

spiracles - pores on the exoskeleton which open and close enabling them to control gas exchange (gases diffusing in and out) & minimise water loss

tracheae - branch throughout the body to deliver gases from spiracles to tracheoles, made of chitin to prevent tracheae from collapsing

tracheoles - tracheae divides into loads of small branches which deliver gases to cells, has tracheal fluid

name the 3 adaptations of tracheoles

large surface area - there are lots and lots of highly branched tracheoles

short diffusion distance - tracheoles have thin walls

maintains steep concentration gradient - oxygen diffuses into cells carbon dioxide diffuses out of cells

what is found in tracheoles which enables the diffusion of oxygen

tracheal fluid

what is tracheal fluid

thin layer of water which allows oxygen to dissolve and then diffuse directly into body cells

how does gas exchange occur at the treacheoles

oxygen dissolves in tracheal fluid and diffuses INTO body cells, carbon dioxide diffuses into tracheoles OUT of body cells to be removed from body

what is another method of ventilation used by active insects

relax and contract abdominal muscles which creates a pumping motion which pumps air for ventilation

when an insect is flying what happens to the muscles

relax and contract much more rapidly causing muscle cells to respire anaerobically

what does anaerobic respiration produce

lactate

what happens to the lactic acid when anaerobic respiration occurs for a while

lactic acid begins to accumulate

what is the impact of lactic acid accumulating

it lowers the water potential of cells causing the water from the tracheal fluid in the tracheoles to move into the cells via osmosis

lower volume of tracheal fluid = more of the tracheole surface is exposed to air = increased surface area for oxygen to diffuse into cells