**4.3 Gas exchange** Flashcards
Alveoli
- Air sacs found at the end of bronchioles which provide larger SA.
Bronchi
- 2 airways branching out from trachea, leading to smaller bronchioles.
Bronchioles
- Branch from bronchi and end at alveoli.
Buccal cavity
- Space in mouth of bony fish.
Counter current flow
- Adaptation for gaseous exchange in bony fish.
- Blood in gill and water go in opp directions.
- Maintains steep O2 conc. gradient.
Diaphragm
- Large sheet of muscle under lungs to create pressure changes for ventilation.
What happens during expiration (diaphragm, ribs, thorax, air)?
- Diaphragm relaxes and resorts to dome.
- External intercostal muscles relax, ribs move in + down.
- Volume of thorax decreases + thoracic pressure exceeds air pressure.
- Air moves out of trachea.
External intercostal muscles + what type of air movement are they involved in?
- Muscles found between the ribs on the outside.
- Forced + quiet inhilation.
Gill filaments
- Small divisions in the gills in fish that extend off the gill arch.
Gill lamellea
- Small protrusions on gill filaments to increase SA for gas exchange.
Gill plates
- Large stacks of gill filaments.
Goblet cells
- Specialised cells that secrete mucus onto trachea lining.
- Mucus traps harmful substances (e.g. microorganisms) preventing them from entering the lungs.
Guard cells
- Usually found in pairs, specialised to control opening + closing of stomata.
What happens during inspiration (diaphragm, ribs, thorax, air)?
- Diaphragm contracts + flattens.
- External intercostal muscles contract, moving ribs up + out.
- Volume of thorax increases + thoracic pressure falls below air pressure.
- Air moves into trachea.
Internal intercostal muscles + what type of air movement are they involved in?
- Set of muscles between ribs on inside.
- Forced exhalation.
Lenticels
- Porous + loosely packed sections of tissue found on surfaces of plants that allows for gas exchange.
Opercular cavity
- Space exterior to gills which is below buccal cavity of bony fish.
Operculum
- Bony flap which covers gills of fish.
Sphincters
- Rings of muscles that surround the openings to spiracles.
- Control size of opening to maintain balance between gas exchange + water loss.
Spiracles
- Small openings on the surface of insects that allow for exchange of gases with their environment.
Stomata
- Small openings in leaves or stem of a plant that can be opened or closed by guard cells in response to varying conditions.
Tracheae (insects)
- Tubes leading from spiracles to tracheoles.
Ventilation
- Process of exchanging air between lungs + atmosphere.
Where does gas exchange take place in mammals?
- Lungs.
What is Boyle’s Law?
- Volume is inversely proportional to pressure.
Where does oxygen move from the alveoli via diffusion?
- Into capillaries.
How are alveoli and capillaries specialised?
- Large SA.
- 1 layer of flattened epithelial cells.
- Large conc gradient.
Insects have an exoskeleton, what does this prevent them from doing?
- Taking oxygen through their skin via diffusion.
How does oxygen enter insects?
- Through openings called spiracles that are opened + closed by sphincters.
Why does gas exchange not happen in the trachea of insects?
- Lined w/ rings of chitin ∴ impermeable.
Why do the trachea of insects have chitin rings?
- To stop trachea from collapsing.
What is the journey of gas in an insect?
- Spiracles.
- Trachea.
- Tracheoles.
Where does gas exchange occur in insects?
- Tracheoles.
What can happen in tracheoles that can slow down diffusion?
- Water can build up in the bottom.
How is water removed from the tracheoles in active insects?
- Lactic acid builds up in cells reducing their water potential.
- Osmosis —> water into cells.
- ∴ gas exchange can occur.
How do some active insects ventilate their respiratory systems?
- Mechanical ventilation - by pumping abdomen.
- Air reserves.
Why is gas exchange harder for fish?
- Water is more dense + contains less O2 than air does.
What are gills made of?
- Filaments covered in folds called lamellae.
How do gills not stick together?
- Continuous movement of water - increased SA.
What is the flap that covers the gills called?
- Operculum.
How does the process of gas exchange in fish occur?
- Floor of mouth opened + operculum closes.
- Floor of mouth raised to increase pressure (valves stops water escaping).
- Increased pressure forces operculum to open + water forced over gills.
How is a conc. gradient maintained between the water and capillaries in the lamellae?
- Countercurrent exchange system.
What is a countercurrent exchange system in fish?
- Water on gills and blood in gills flow in opposite directions.
- Maintains steep conc. gradient over entire gill filament.
What are the layers of a leaf?
- Waxy cuticle.
- Upper epidermis.
- Palisade mesophyll.
- Spongy mesophyll.
- Lower epidermis (guard cells + stomata).
What is the function of the waxy cuticle?
- Prevents water loss.
What is the purpose of the upper epidermis?
- Transparent it allow max. amount of sunlight through to cells w/ chloroplasts.
What is the purpose of the palisade mesophyll?
- Cells stacked vertically to fit as many as possible.
- These cells contain the most chloroplasts.
What is the purpose of the spongy mesophyll?
- Air spaces provide large SA for gas exchange.
What is the purpose of the lower epidermis (guard cells + stomata)?
- Guard cells control stomata to prevent excessive water loss.
- Guard cells thicker on side adjacent to stomata to enable opening + closing.
What are the 2 processes that plants undergo?
- Photosynthesis + respiration.
Do the stomata open or close during the day?
- Open - conditions favorable for photosynthesis.
- CO2 in, O2 out.
How do the stomata open?
- Ions (mainly K+) move into guard cells by active transport.
- Causes water to move in by osmosis due to water potential decrease.
- Causes cells to go turgid + swell ∴ stomata open.
What are lenticles
- Areas of loosely arranged cells which act as a pore to allow gas exchange in lignified (woody) plants.
