gas exchange in insects Flashcards
what is a spiracle
an external opening or pore that allows air in or out of the tracheae
what is tracheal fluid
the fluid found at the ends of the tracheoles in the tracheal system
what is the tracheal system
a system of air filled tubes in insects
what is the problem with many active insects
they have high oxygen requirements but htey dont have a tough exoskeleton through which little or no gaseous exchange can take place. they don’t have blood pigments that can carry oxygen
how has the gaseous exchange system of insects evolved
to deliver oxygen directly to the cells and to remove the carbon dioxide in the same way
what are the small openings along the thorax and abdomen
spiracles
what enters and leaves via the spiracles
air enters and leaves the system through the spiracles but water is also lost
what do insects need to maximise and minimise
maximise the efficiency of gas exchange and minimise the loss of water
what happens to the spiracles when insects are inactive and oxygen demands are low
they close
what happens to the spiracles when the oxygen demand is raised
most of the spiracles open
what are the tracheae
the largest tubes of the insect respiratory system and they carry air into the body. they run into and along the body of the insect
what are the tracheae lined by
chitin
what does chitin do
keeps the tracheae open if they are bent or pressed. it makes up the cuticle.
why does little gas exchange take place in the tracheae
the chitin lining the tracheae is relatively impermeable to gases
where does most gas exchange occur
in the tracheoles
what is the width of the tracheoles
0.6-0.8µm
why does most gas exchange take place in the tracheoles
the tracheoles are single, elongated cells with no chitin lining. this means they are freely impermeable to gases. the tracheoles are thin so spread throughout the tissues of the insect running between individual cells.
how does diffusion occur in the tracheoles
most of the time air moves along the tracheae and tracheoles by diffusion alone reaching all the tissues. vast numbers of tiny tracheoles give a very large surface area for gaseous exchange. oxygen dissolves in moisture on the walls of the tracheoles and diffuses into the surrounding cells.
where is the tracheal fluid located
at the end of the tracheoles
what does the tracheal fluid do
limits the penetration of air for diffusion
what happens when oxygen demand builds up in the insect
lactic acid builds up in the tissues. this results in water moving out the tracheoles by osmosis exposing more surface area for gas exchange
how is gas exchange controlled by insects
by the opening and closing of the spiracles
where does an insect get all of the oxygen it needs
insects possess an air filled tracheal system which supplies air directly to all respiring tissues
do insects transport oxygen in blood
no
what kind of circulatory system do insects have
an open circulatory system in which the body fluid acts as both blood and tissue fluid
how is circulation affected
by body movements
how does air enter the tracheal system
via a spiracle. the air is transportned into the body through a series of tubes called tracheae
where does gaseous exchange occur
between the air in the tracheole and the tracheal fluid. some exchange can also occur across the thin walls of the tracheoles
what do the tracheae divide into
smaller tubes called tracheoles. the ends of the tracheoles are opened and filled with tracheal fluid
how is more oxygen absorbed when the insect is active
when tissues are active, the tracheal fluid can be withdraw into the body fluid to increase the surface area of the tracheole wall exposed to the air
how do larger insects ventilate their tracheal systems
by movements of the body
what do sections of the tracheal system have
they are expanded with flexible walls
what do the flexible walls of the tracheal system act as
air sacs which can be squeexed by the action of the flight muscles
what does repetitive expansion and contraction of the air sacs do
ventilates the tracheal system
what does movement of the lungs do
alter the volume of the thorax
what happens as the thorax volume decreases
air in the tracheal system is put under pressure and is pushed out of the tracheal system
what happens when the thorax increases in volume
the pressure inside drops and air is pushed into the tracheal system from outside
how can locusts alter the movement of their abdomen
by specialised breathing movements. these are coordinated with the opening and closing of the valves in the spiracles
what happens as the abdomen expands
spiracles at the front end of the body open and air enters the tracheal system
what happens as the abdomen reduces in volume
the spiracles at the rear end of the body open and air can leave the tracheal system
