Lesson 3 - Gas exchange in insects Flashcards
meaning spiracles
openings along the side of the thorax and abdomen of an insect that are the site of the entry and exit of the respiratory gases. They may be opened or closed by sphincters
meaning tracheae
the largest tubes of the insect respiratory system, carrying air directly into the body for gas exchange with the cells. They run both into and long the body of an insect
meaning tracheoles
minute tubes of diameter 0.6 - 0.8 micrometer that are the site of gas exchange in insects. They contain no chitin, so are freely permeable to gases.
describe the issues facing gas exchange in insects
- high oxygen demand
- very active
- their exoskeleton which doesn’t allow gases to pass through
describe the function of chitin in the tracheae
the tracheae are supported by spirals of chitin and hold the tracheae open if they are squashed when the insect moves. However, the chitin makes the tracheae impermeable for gases, so little gas exchange occurs in these tubes
what happens to the sphincters when an insect becomes active
there is a higher oxygen demand, so more spiracles open
what happens inside the trachea when an insect becomes active
When the insect becomes active, lactic acid builds up in the muscle tissue. This affects the osmotic concentration of the cells, and water moves out of the tracheoles into the cells via osmosis. This exposes additional surface area in the tracheoles for gaseous exchange
what is the effect of the tracheoles containing water towards the ends of their lengths
This limits the penetration of the gases by diffusion
what is the function of the opening and closing of the spiracles
- to limit water loss
- to control the rate of gas exchange in an insect
how does the opening and closing of the spiracles control the rate of gas exchange in an insect
it’s coordinated by respiratory centres in the nervous system, which are stimulated by increasing carbon dioxide levels and by lactic acid that builds up in active tissue where there is a lack of oxygen
explain how mechanical ventilation helps very active insects with respiration
when air is actively pumped into the tracheal system, the spiracles open and the insect makes muscular pumping movements of the thorax, abdomen, or both. These ventilation movements change the volume and therefore the pressure inside the body, drawing air in and out of the tracheae and tracheoles
how do collapsible tracheae or air sacs help very active insects with respiration
the collapsible tracheae and air sacs act as air reservoirs. They increase the volume of air moved through the respiratory system. The ventilating movements of the thorax and abdomen inflate and deflate them.
