3.3.2Gas Exchange Flashcards
(16 cards)
Describe the tracheal system of an insect
Spiracles - pores on the surface to allow diffusion
Trachea - large tubes full of air that allow diffusion
Tracheoles - smaller beaches from tracheae, they allow gas exchange
How does gas exchange occur within an insect
- short diffusion distance as the tracheoles have thin walls
-many branched trancheoles, leading to a short diffusion distance and a large SA
-air moves in/out due to the contraction of abdominal muscles which causes the pressure to change, this maintains a conc gradient
-fluid in the end of tracheoles are drawn into tissues by osmosis my exercise(lactate from anaerobic respiration causes the water potential to drop). As this fluid is removed, air fills the tracheoles. This means the final stage of gas exchange is in the gas stage which is faster than that through liquid.
Structural differences that limit water loss in gas exchange (insects)
Thick exoskeleton- high diffusion distance reducing water loss through evaporation
Spiracles can open to allow air in but close to stop water escaping via evaporation
Hairs around the spiracles trap moist air, reducing the water potential gradient so less water is lost via evaporation.
How are gills adapted form gas exchange
Large SA- due to many filaments covered in lamellae
Short diffusion pathway - thin lamellae wall
Maintains conc gradient - lamellae have a large number of capillaries.
How does counter current flow work in gills
Blood and water flow in opposite directions (over lamellae)
So O2 conc is always higher in water (than blood)
Maintains a conc gradient
Difffusion occurs along the whole lamellae
How are leaves adapted to gas exchange
Lost of stomata - large SA for gas exchange when opened by guard cells
Spongey mesophyll has air spaces- this allows a large SA for gases to diffuse through
Short diffusion distance - due to stomata being thin
Layers of a leaf (top to bottom)
Waxy cuticle
Upper epidermis
Palisade mesophyll
Spongey mesophyll(air pockets)
Lower epidermis (stomata / guard cells)
Structural differences that limit water loss in gas exchange (plants)
Thick waxy cuticle - increases diffusion distance so less water loss via evaporation
Hairs - to trips water vapour, this reduces the water potential so less evaporation
Spines / needles - reduces SA:V ratio
Structure of gas exchange in humans
Trachea, bronchi, bronchioles, alveoli(air sacs)
How is alveoli adapted for gas exchange
Short diffusion distance - 1 cell thick,
Large SA:V
Preamble to allow diffusion
Maintains conc gradient due to large network of capillaries (good blood supply)
How does gas exchange occur in the lungs
Oxygen diffuses from the the alveoli’s into the blood down the conc gradient across the alveolar epithelium and across capillary endothelium
Explain inspiration
Diaphragm muscles contract -flatten
External intercostal muscles contract and internal relax, rib cage pulled up and out
V increases and pressure decreases
Air moves into lungs down pressure gradient
Explain expiration
Diaphragm relaxes - moves up
External muscles relax, internal contract, rib cage down and in
V decreases , pressure increases
Air moves out of lungs down pressure gradient
Why is expiration normally passive at rest
Internal intercostal don’t normally need to contract
Expiration is aided by elastic recoil in the alveoli
How does lung disease effect the rate of gas exchange
Alveolar tissues is thickened (fibrosis) so grater diffusion distance
Alveolar wall break down - reducing SA
Reducing lung elasticity- lungs expand and less recoil. This reduces conc gradient.
How does fibrosis and asthma affect ventilation
Fibrosis/build up of scar tissue - reduced lung elasticity, lungs expand less. Reduction in volume in each breath (tidal volume). Reduction in max volume of breathed in and out in 1 breath
Asthma/inflamed bronchi - narrow airways reducing airflow in and out of lungs. This reduces max volumes being breathed in and out.
