exchange surfaces Flashcards
Why do some organisms need specialised exchange surfaces?
- Larger organisms have a smaller SV/Vol ratio and so every cell is not in contact with the external environment and cannot get what it needs by simple diffusion
- So some organisms need specialised exchange surfaces to supply each cell with what it needs
What are the four features of a food exchange surface?
- Large surface area
- Thin layers
- Good blood supply
- Ventilation
How does a large surface area a feature of a good exchange surface?
- Provides the area needed for exchange and overcome the limitations of the SA/Vol ratio of large organisms
- Root hair cells and villi
How are thin layers a feature of a good exchange surface?
- The diffusion pathway for the gasses are short and makes the process fast and efficient
- Alveoli and villi
How is a good blood supply a feature of a good exchange surface?
- Ensures that gases are constantly delivered to and removed from the exchange surface, maintaining a steep concentration gradient for a faster diffusion rate
- Alveoli, villi, fish gills
How is ventilation a feature of a good exchange surface?
- Helps maintain concentration gradient and makes the process more efficient
- Ventilation : a flow of water carrying dissolved gases
What is the relationship between sa and volume?
The bigger the organism, the smaller the sa/vol ratio
What are the four structures involved in the mammalian gaseous exchange system?
- Trachea
- Bronchi
- Bronchioles
- Alveoli
What is the function of the trachea?
Carries air into the lungs, it branches into bronchi
How are the tissues related to the function of the trachea?
- Supported by C shaped cartilage rings
- Lined with ciliated epithelium
- Goblet cells
- Contains smooth muscle and elastic fibres
What is the function of the bronchi?
Carries air into both lungs, branches into bronchioles
How are the tissues related to the function of the bronchi?
- Supported by full rings of cartilage
- Lined with ciliated epithelium and goblet cells
- Contains smooth muscle and elastic fibres
What is the function of the bronchioles?
To carry air to the alveoli
How are the tissues related to the function of the bronchioles?
- Walls made up of smooth muscle and elastic fibres
- Lined with ciliated epithelium and goblet cells
What is the function of the alveoli?
Site of gaseous exchange
How are the tissues related to the function of alveoli?
- Composed of squamous epithelium
- Walls contain elastic fibres
What is the function of rings of cartilage?
To prevent collapse during inspiration
What is the function of smooth muscle?
To control the diameter of the trachea, bronchi, and bronchioles
- Changes the amount of air reaching the lungs to prevent harmful substances from involuntary entering due to an allergic reaction
What is the function of elastic fibres?
To stretch
- The alveoli as air is drawn in and squeeze as air is drawn out when returning to resting size
- Allows airways to return to original lumen size once smooth muscle relaxes
What is the function of ciliated epithelium?
To waft mucus upward to the mouth to be swallowed
What is the function of squamous epithelium?
Allows for rapid and efficient gas exchange
What is the function of goblet cells?
To secrete mucus to trap pathogens
Describe the active process of inspiration
- The external intercostal muscles contract moving the ribcage upwards and outwards
- The diaphragm MUSCLE contracts and moves downwards
- The volume of the thorax is increased by these two actions
- The pressure in the chest decreases and is lower than the atmospheric pressure, so air is drawn into the lungs
Describe the passive process of expiration
- The external intercostal muscles relax and the ribcage falls under its own weight
- The diaphragm MUSCLE relaxes and moves upwards
- The volume of the thorax is decreased by these two actions
- The pressure in the chest increased and is higher than the atmospheric pressure, so air is forced out of the lungs
Why is inspiration an active process but expiration is passive?
During expiration, energy is not required to push air out of the lungs and so is passive
During inspiration, the muscles must contract to draw air into the body and so is active
How are the lungs specially adapted to gas exchange?
- Good blood supply
- Thin walls - squamous epithelium cells
- Ventilation - constant movement of co2 and o2
How does a spirometer work?
- A person breathes through a tube connected to the oxygen chamber
- As the person breathes in and out, the lid of the chamber moves up and down
- A trace is drawn on a rotating drum of paper
- An upwards slope indicated the person breathing out as the volume in the chamber increases
- A downwards slope indicated the person breathing in as the volume in the chamber decreases
How do you ensure that the results of the spirometer are valid?
- No air leaks/air tight
- The person is wearing a nose clip
What precautions must be taken when using a spirometer?
- Patients should be healthy and free of asthma
- Sterilised mouthpiece
- Fresh and functioning soda lime
What are the features of fish during gas exchange?
- Operculum - covers gill, gill
- Gill arch - cartilaginous structure that provides support for the filaments
- Filaments - thread-like structures, composed of many lamellae, that spread out and create as much surface area as possible
- Lamellae - disk-like structures stacked along the filaments that contain the capillaries where gas exchange takes place
What are the challenges of gas exchange in water for fish?
- Water is denser and more viscous than air, so slower diffusion of oxygen
- Water has less oxygen than air
- Bony fish are very active so have high oxygen demands
How are fish adapted for gaseous exchange?
- Counter current exchange system
- Gill adaptations
How does ventilation help gas exchange in fish when their mouth is open?
- Buccal cavity volume increases
- Pressure decreases
- Water is sucked into the fish
How does ventilation help gas exchange in fish when their mouth is closed?
- Buccal cavity volume decreases
- Pressure increases
- Water is forced out across gill filament
How are fish gills adapted?
- Rich blood supply
- Large SA
- Thin layers
- Adjacent gill filaments overlap - inc resistance to water - slow movement - inc gas exchange
How do the fish have an increased surface area?
Gill filaments increase sa
Gill filaments covered in lamellae which increase sa
How are gill plates adapted?
They have a good blood supply through the capillaries and have a thin surface for efficient diffusion
What are the two conflicting needs of insects during gas exchange?
- Maximising gas exchange efficiency
- Minimising water loss - waterproof cuticle covering exoskeleton
What are the main structures involved in gas exchange in insects?
- Tracheae - air filled tubes branching throughout the body
- Tracheoles - fine branches of tracheae that deliver gases to cells
- Spiracles - external openings on the exoskeleton along the abdomen and thorax
How are the tracheae adapted?
- Reinforced with spirals of chitin to prevent collapse and gas exchange
- Multiple tracheae to increase sa
How are the tracheoles adapted?
- Penetrate directly into tissues - reduce gas diffusion distance
- Thin walls - reduce gas diffusion distance
- Highly branched - maximises sa
- Not reinforced with chitin - allows gas exchange
- Tracheal fluid at the ends - allows oxygen to dissolve to aid diffusion and reduces water loss
How are spiracles adapted?
Open and close - controls gas exchange with the atmosphere and minimise water loss
