Gas exchange Flashcards
Surface area : Volume ratio
relationship between the size of an organism or structure and its surface area to volume ratio plays a significant role in the types of adaptions an organism will have.
allows transport across surface more efficient in organisms.
calculate
-surface – multiply length by width then times by how many sides.
-SA:VR calc the volume- normally length x width x height.
small organisms SA:VR
-small organisms have a very large surface area in comparison to their volume
-this means there is a big surface for the exchange of substances, but there is also smaller distance from the outside of the organism to the middle of it
- as a result very small organisms can simply exchange substances across its surface by diffusion.
larger organisms SA:VR
why does larger organisms having a higher metabolic rate mean that they need specific adaptions.
-larger organism = smaller the SA compared to ratio
-therefore larger the distance from the middle to the outside
-larger organisms will typically have a higher metabolic rate, which demands efficient transport of waste out of cells and reactants into cells.
because of this they have adaptions that help make their exchange across surfaces more efficient.
some examples that larger organisms may have to allow efficient exchange across surfaces
-villi and microvilli - absorption of digested food
-alveoli and bronchioles- for efficient gas exchange in animals.
-spiracles and tracheoles - for efficient gas exchange in terrestrial insects
-gill filaments and lamellae- for efficient gas exchange in fish
-thin wide leaves- for efficient gas exchange in plants
-many capillaries- for efficient exchange at tissues.
the key structures in the human gas exchange system
labelled diagram in notes
-alveoli
-bronchioles
-bronchi
-trachea
-lungs
what do we need to know for ventilation within the human gas exchange system
labelled diagram in notes
-diaphragm
-intercostal muscles
ventilation
labelled diagram in notes.
-exhaling and exhaling in humans
-controlled by the diaphragm muscle and the antagonistic interaction between the external and internal intercostal muscles.
how does the diaphragm and antagonistic internal and external muscles work to cause inspiration and expiration.
external intercostal muscles.
inspiration- contract to pull the ribs up and out
expiration - realx
how does the diaphragm and antagonistic internal and external muscles work to cause inspiration and expiration.
internal intercostal muscles
inspiration - relax
expiration- contract to pull the rib down and in
how does the diaphragm and antagonistic internal and external muscles work to cause inspiration and expiration.
diaphragm
inspiration - contracts to move down and flattens
expiration - relaxes to move up and dome.
how does the diaphragm and antagonistic internal and external muscles work to cause inspiration and expiration.
air pressure in the lungs
Inspiration- initially drops as air moves in it rises above atmospheric pressure
Expiration - initially greater than atmospheric pressure
Drops as air moves out
how does the diaphragm and antagonistic internal and external muscles work to cause inspiration and expiration
Lung volume
Inspiration-increases
Expiration - decreases
how does the diaphragm and antagonistic internal and external muscles work to cause inspiration and expiration
Movement of air
Inspiration- air moves into lungs as the atmospheric pressure in the thorax is higher than that of the atmosphere
Alveoli when is the air received and where is it came from
Diagram in notes
-once the air has travelled down the trachea bronchi and bronchioles to the alveoli gas exchange occurs between the alveolar epithelium and the blood.
Alveoli
Adaptions
Diagram in notes
-tiny air sacs
-300 in each human lung (large amount)
Creates a larger surface area for gas exchange
-the alveolar epithelial cells are very thin to minimise diffusion pathway
-each alveolus is surrounded by a network of capillaries to remove exchanged gases and therefore maintain a concentration gradient
Gas exchange in fish
-fish are waterproof and they have a small SA:VR this is why the require a gas exchange surface (gills)
Fish obtain oxygen from the water but there is 30 times less oxygen in water than in air
So they have a special adaption (countercurrent flow) to maintain the concentration gradient to enable diffusion to occur.
Fish gill anatomy
Diagram in notes
-there are four layers of gills on both sides of the head
These gills are made up of stacks of gill filaments
Each gill filament is covered in gill lamellae positioned at right angles to the filament this creates a larger surface area
When fish open their mouths water rushes in and over the gills and then out through holes in the sides of their head.
Adaptions for gas exchange in fish
- to create a larger surface area to volume ratio for diffusion there are many gill filaments covered in many gill lamellae
-there is a short diffusion distance due to a capillary network in every lamellae and all gill lamellae are very thin
-the concentration gradient is maintained by the countercurrent flow mechanism
What is Countercurrent flow mechanism
Diagram in notes
-when water flows over the gills in the opposite direction to the flow of blood in the capillaries
What does countercurrent flow ensure
Diagram in notes
That equilibrium is not reached
This ensures that a diffusion gradient is maintained across the entire length of the gill lamellae
gas exchange in terrestrial insects
-exoskeleton =made from hard fibrous material for protection
and a lipid layer to prevent water loss.
-therefore they need a gas exchange system.
-they do not have lungs but instead have a tracheal system.
the tracheal system
whats involved?
- trachea
-tracheoles
-spiracles
tracheal system
spiracles
-round valve like openings
-running along the length of the abdomem.
-oxygen and carbon dioxide enter and leave via the spiracles
-the trachea attaches to these openings
tracheal system
the trachea
-a network of internal tubes
-the tubes have rings of cartliage (tough connective tissue) within them to strengthen them and keep them open.
