Exchange surfaces Flashcards
what are the features of effective exchange surfaces
increased surface area
thin layers
good blood supply
ventilation to maintain diffusion gradient
how are alveoli adapted for gas exchange
- large SA
-barrier is cell membrane of squamous epithelia, they are permeable to gasses, moisture - low diffusion gradient as squamous epithelia are thin and flat
-steep diffusion gradient maintained: blood flow brings more CO2 from tissues
what happens during inspiration
intercostal muscles contract
ribs are pulled upwards and outwards
diaphragm contracts and flattens
- increased volume in thorax
- reduced air pressure
air is forced into lungs
what happens during expiration
the intercostal muscles relax
ribs move downwards and inwards
diaphragm relaxes and moves up
- decreased volume of the thorax
-increased air pressure
air forced out of lungs
what are the structures within trachea
- has c-shaped rings of cartilage for support and to ensure the trachea does not collapse
- has goblet cells to release mucus to trap dust and pathogens which is then swept up by the ciliated epithelial cells
- there is smooth muscle within the tracheal wall, which contracts if there are harmful substance detected in the air, this reduces air flow
- there are also elastic fibres, this enables the lumen to dilate when the smooth muscle relax
How does having a large surface area aid exchange surfaces?
Allows more substances to travel across at a time, increasing exchange rate
How does being thin aid exchange surfaces?
Allows substances to travel across them more quickly, increasing exchange rate
How does having a good blood supply aid exchange surfaces?
Allows optimal concentration gradient to be maintained by bringing/taking away substances quickly
How does having good ventilation aid exchange surfaces?
Allows a steep concentration gradient to be maintained
What are the walls of alveoli made up of?
Squamous epithelial cells, some collagen and elastic fibres made from elastin
What is the purpose of the elastic tissues in alveoli?
They allow the alveoli to stretch when air enters, and recoil in order to help force air out
what are two methods of measuring volume of gas drawn in and out of lungs
1- peak flow meter
2- a spirometer
define tidal volume
it is the volume of air that moves into and out of the lungs with each resting breath
define vital capacity
Maximum volume of air that can be inhaled and exhaled
why does a spirometer contain sodalime
to absorb the CO2 from the users air supply
What is the inspiratory reserve volume?
The amount of air you can breathe in over and above a normal inhalation
What is expiratory reserve volume?
The extra amount of air you can force out of your lungs over and above the normal tidal volume of air you breathe out
What happens when a fish opens its mouth?
The operculum closes over the gills, the buccal cavity expands and the opercular valve (to the outside) is closed. This means that the pressure in the mouth drops, and water rushes in
What is residual volume?
The volume of air left in your lungs when you have exhaled as hard as possible
name the structures involved in gas exchange in insects
spiracles
tracheae
tracheoles
muscle tissues
What happens when a fish closes its mouth?
The cheeks move inward, causing pressure in the mouth to increase and forcing water over the gills, also causing the opercular valve and operculum to open
What is the counter-current flow system and why is it used by fish?
It is where fish have blood flowing one way and water flowing the other. This is so that the concentration gradient of CO2 and oxygen is maintained throughout the gill, thus maximising the efficiency of diffusion
explain challenges insects face with gas exchange
- exoskeleton made of chitin is impermeable to gases
- no blood pigments, gases cannot be carried in blood
- high energy needs
describe how spiracles are involved in gas exchange
opening in the body surface that can be opened and closed by sphincter muscles.
-when inactive, the insects oxygen demands are low so the spiracles are closed
- when oxygen demands are raised or CO2 levels build up then spiracles open
explain how the tracheae is involved in gas exchange
- these are the largest tubes that carry air into and along the boy
-the tubes are lined with spiral of chitin, which keeps them open, and is impermeable
-little gas exchange takes place here
explain how tracheoles are involved in gas exchange
- they single elongated cells, with no chitin
- because of their small size they run between individual cells
-this is where most of the gaseous exchange takes place
explain how muscles cells are involved in gas exchange in insects
- surrounded by tracheal fluid where gases can dissolve and diffuse into muscle cells
for larger insects what are alternative methods of increasing gas exchange
- mechanical ventilation of the tracheal system
- collapsible enlarged tracheae or air sacs
outline how insects use mechanical ventilation
-air is actively pumped into the system by muscular pumping movements of the thoraw and or the abdomen
- this changes the volume of the body cavity creating pressure differences
- happens via wing movements
outline how insects use air sacs in gas exchange
- the collapsible enlarged trachea or air sacs act as reservoirs
- they inflate and deflate with pumping movements
- have thin collapsible walls
Apart from counter-current flow system, what is another adaption in fish which helps maximise gas exchange effectiveness?
The tips of their gill filaments overlap, increasing the resistance to the flow of water and slowing down water movement, helping maximise the time that diffusion can occur for
As well as increasing surface area, what is the secondary purpose of a fish’s lamallae?
To direct the flow of water in the gills
Why can’t fish breathe in and out by ventilation?
Because water is much denser and more viscous than air, and has a much lower oxygen content, so it saves energy for them to move water in 1 direction only
