7 - Exchange Surfaces Flashcards
Why can’t fish breathe in and out via ventilation?
Water is denser, more viscous and has a lower oxygen content than air, so requires too much energy to be efficiently moved by a 2-way ventilation system
Do prokaryotes need specialised exchange surfaces?
No as they are small enough to get the resources they need via osmosis, diffusion etc.
Why do larger, eukaryotic organisms need specialised exchange surfaces?
Because they have greater metabolisms so need more resources and have lower SA:V ratios so cannot get all of these resources via simple diffusion, osmosis etc. as the substances need to travel further to get to our internal cells
What are 4 things all good exchange surfaces should have/be?
- Large surface area 2. Thin 3. Good ventilation 4. Good blood supply
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
Why can a single-celled organism only reach a certain size?
Because any larger and it’s SA:V ratio would be too small for it to support its metabolism when only transporting materials via diffusion, osmosis etc.
What is an exotherm?
A cold-blooded organism
What is an endotherm?
A warm-blooded animal
Why do mammals need excellent exchange surfaces?
Because they have large metabolisms
What is the exchange surface area of the lungs?
Around 55-57 metres squared
What is the biological name for the mouth?
The buccal cavity
What is the purpose of the nasal cavity?
Increases the temperature and moisture content of inhaled air. It’s hairy, mucus-secreting lining also traps pathogens and irritants
What is the membrane on the surface of the lungs called?
Pleural Membrane
What are the muscles between the ribs called?
Intercostal muscles
What is the sequence of airways that air passes down?
Mouth/Nostril—>Buccal/nasal cavity—>Trachea—>Bronchus—>Bronchioles—>Alveoli
Which bones protect the chest cavity?
The ribs
Why does the trachea have c-shaped rings of cartilage?
To prevent it from collapsing due to pressure changes in the lungs
What two types of cells is the trachea lined by?
Goblet and Ciliated Epithelial cells
What is the purpose of goblet cells?
They secrete mucus, which traps dust and microbes
What is the purpose of ciliated epithelial cells?
They are adjoining to goblet cells, and use their cilia to sweep mucus and whatever is trapped within it out into the throat
What is the structure of the bronchi?
Similar to the trachea and with rings of cartilage
Which bronchioles have cartilage?
Those with a diameter greater than 1mm
What is the purpose of smooth muscle cells contained in the walls of the bronchioles?
To allow them to dilate and constrict
Are ciliated cells present in the bronchioles and alveoli?
No
Is gas exchange possible in the bronchioles?
Some, through the flattened epithelial lining
What is the diameter of alveoli?
200-300 micrometers
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
Where is lung surfactant found?
Coating the inside of alveoli
What are the 2 purposes of lung surfactant?
Prevent the alveoli from collapsing and help prevent water loss
What is the purpose of external intercostal muscles?
When they contract, they lift the ribcage up and out (during inhalation)
What is the purpose of internal intercostal muscles?
They push the ribcage downwards and inwards during forced exhalation
What 2 steps occur during inspiration?
- Intercostals contract, making ribcage move upwards and outwards 2. Around the same time, diaphragm contracts and flattens
What effect does the movements of the diaphragm and intercostal muscles have during inspiration?
Increases the volume of the chest cavity, causing its pressure to become lower than atmospheric pressure, meaning air moves into the lungs
What 2 steps occur during expiration?
- The intercostal muscles relax, making the ribcage move downwards and inwards 2. The diaphragm relaxes and expands into a dome shape
What effect does the movements of the diaphragm and intercostal muscles have during expiration?
They decrease the volume of the chest cavity, causing its pressure to increase to more than atmospheric pressure and, with the help of the recoil of the elastic fibres in the alveoli, forcing air out of the lungs
What are 3 methods of measuring the volume of gas drawn into the lungs?
- A peak flow meter 2. A vitalograph 3. A spirometer
What is a peak flow meter?
A plastic tube with an analog measuring device to record peak flow rate, which you blow into. Sharp exhalation needed.
What is a vitalograph?
Essentially the same thing as a peak flow meter but with a digital data logger which produces a graph of force over time as well as ‘forced expiratory volume in 1 second’
How does a spirometer work?
It is a lid bobbing on a tank of water. A person puts in a mouthpiece (whilst wearing a nose clip) attached to a tube which leads into the water. Their breathing thus causes the lid to bob up and down, and it is attached to a pen which creates a trace on a revolving drum of paper
Why does a spirometer have a canister of soda lime?
To filter the CO2 from the user’s limited air supply so that they don’t suffer CO2 poisoning
Why does a person using a spirometer wear a nose clip?
To ensure that the flow of air occurs only through their mouth, thus allowing for accurate readings
What is tidal volume?
The amount of air which moves into and out of the lungs with each resting breath
How much is the typical tidal volume for an adult?
~500cm^3, or around 15% of vital capacity
What is vital capacity?
The amount of air that can be breathed in when the strongest possible exhalation is followed by the strongest possible inhalation
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 is residual volume?
The volume of air left in your lungs when you have exhaled as hard as possible
Can residual volume be measured directly?
No
What is total lung capacity?
Vital capacity plus residual volume
What is inspiratory capacity?
Total volume of air taken in by deepest possible inhalation following normal exhalation
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
Why do fish gills have a vivid red colour?
Because they contain many capillaries
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 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
Why can’t fish breathe in air?
Without water the gill structures collapse, meaning that their exchange surface area is not large enough to keep the fish alive.
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
What is the general structure of the gills in terms of gill arches, gill filaments and lamellae?
Cylindrical gill arch with arteries (containing deoxygenated blood) and vessels (taking oxygenated blood from the gills. These have 2 rows of gill filaments off them, which are have lamellae crossing them to increase surface area
What, briefly, 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
What is a spiracle?
A small opening in the exoskeleton of an insect’s abdomen and thorax, which it uses to exchange gases with the atmosphere
What is a spiracle sphincter?
The things which an insect uses to open and close its spiracles, allowing it to close them when oxygen demands are low to reduce water loss
What are trachea (in insects)?
Small tubes (<1mm) which lead away from spiracles.
How are insect spiracles kept open?
By spirals of the tough polysaccharide chitin
What diameter are insect tracheoles?
0.6-0.8 micrometers
What are insect tracheoles?
Smaller tubes which branch off from the trachea and run in between individual cells to give a very large surface area
Do tracheoles have chitin?
No, in order to maximise gas permeability
What is tracheal fluid?
Fluid found near the end of tracheoles. Gases can dissolve into it and then diffuse across to cells. However, it can also move out of the tracheoles by diffusion if necessary by osmosis (usually due to lactic acid buildup) to expose a greater surface area in them for diffusion to occur across.
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
What 2 adaptations do insects with high energy demands have to maximise gas exchange?
- Some can actively pump air in and out of their body by moving their thorax and/or abdomen 2. Some have internal air sacs which can be inflated and deflated by movement of the thorax and abdomen in order to increase the volume of air which moves
What are insect tracheoles?
Smaller tubes (0.4-0.6 micrometers in diameter) which branch off from trachea and run in between individual cells
