gas exchange Flashcards
what is fick’s law?
surface area x difference in conc / diffusion distance
name three features of an efficient gas exchange system
● large surface area
● short diffusion distance
● steep conc gradient (maintained by blood supply or ventilation)
what is ventilation?
breathing
what is the trachea?
wind pipe
what is the thoracic cavity?
space where the lungs are
explain the human gas exchange system
● as you breathe in, air enters trachea
● trachea splits into 2 bronchi
● each bronchus branches off into smaller tubes called bronchioles
● bronchioles end in small air sacs called alveoli
● ribcage, intercostal muscles and diaphragm work together to move air in and out
explain inspiration
● external intercostal muscles contract
● ribcage - moves upwards and outwards
● diaphragm contracts to flatten
● increasing volume of thoracic cavity
● as volume increases, lung pressure decreases (to below atmospheric pressure)
● air flows down the trachea and into lungs down pressure gradient
what does inspiration require?
energy (active)
explain expiration
● external intercostal and diaphragm muscles relax
● ribcage moves downward and inwards
● diaphragm becomes curved
● volume of thoracic cavity decreases, causing pressure to increase (to above atmospheric pressure)
● air forced down pressure gradient and out of lungs
what does expiration not require?
energy (passive)
explain forced expiration
● external intercostal muscles relax
● internal intercostal muscles contract
● pulling ribcage further down and in
● movement of 2 sets of intercostal muscles are antagonising
what are alveoli made from?
alveolar epithelium
what is the alveolar epithelium made of?
a single layer of thin, flat squamous cells
how does human gaseous exchange happens in the alveoli?
● oxygen diffuses out alveoli, across the alveolar epithelium and capillary endothelium
● into haemoglobin in red blood cells
● carbon dioxide diffuses from blood across capillary endothelium and alveolar epithelium and into alveoli and is breathed out
● movement happens down a diffusion gradient
what is the capillary endothelium?
type of epithelium that forms the capillary wall
how does human gaseous exchange happens in the alveoli? (simplified)
● oxygen - trachea - bronchi - bronchioles - alveoli
● happens down a pressure gradient
● alveoli - diffuse across alveolar epithelium and capillary endothelium - capillary - haemoglobin in blood
● happens down a diffusion gradient
how are alveoli adapted for gas exchange?
● short diffusion distance - alveolar epithelium is made of squamous cells (thin exchange surface)
● large surface area - large number of alveoli means there’s a large surface for gas exchange and folds in alveolar epithelium
● steep concentration gradient of O2 and CO2 between alveoli and capillaries
● capillaries give good blood supply
what is the composition of gases inhaled?
● higher conc of O2
● N2 stays the same
● lower conc of CO2
what is the composition of gases exhaled?
● lower conc of O2
● N2 stays the same
● higher conc of CO2
what is tidal volume?
● tidal volume is the volume of air in each breath
● average 0.4 - 0.5dm^3
what is forced expiratory volume (FEV1)?
maximum volume of air that can be breathed out in 1 second
what is forced vital capacity (FVC)?
maximum volume of air that can be breathed forcefully out after a deep breath
what is pulmonary ventilation?
● volume of air ventilated by the lungs in 1 minute
● PV (dm^3) = tidal volume x ventilation rate
what is ventilation rate?
● number of breaths per minute
● average 15
how does pulmonary fibrosis slow gas exchange
● scar tissue makes alveoli thicker
● reduces elasticity of alveoli
● increases diffusion distance
how does TB slow gas exchange
● scar tissue makes alveoli thicker
● reduces elasticity of alveoli
● increases diffusion distance
how does asthma slow gas exchange
● tidal volume reduced
● decreases conc gradient
how does lung cancer slow gas exchange
● tidal volume reduced
● decreases conc gradient
how does emphysema slow gas exchange
● reduced elasticity
● prevents exhalation
● decreases conc gradient
correlation doesn’t equal
causation
why can’t in
what is a spiracle
● opening in the exoskeleton of insects body
● most of the time closed to avoid water loss
what is an insects exoskeleton?
● made of chitin
● impermeable to gases
explain insect gas exchange system
spiracle - tracheal tubes - tracheoles - respiring cells
how are insects adapted for gas exchange?
● highly branched tracheoles - increases surface area
● tracheoles have thin walls - short diffusion distance
● cells constantly respiring & abdominal pumping (a form of ventilation) - maintains conc gradient
how do insects control water loss?
● if losing too much water, closes spiracles
● waterproof waxy cuticle and tiny hairs around spiracles - reduce evaporation
where does water flow in fish
water - mouth - water passes across gills
what is the structure of a fish’s gills
● gill arch
● gill filaments attached to gill arch
● gill lamellae on the surface of each gill filament
● gill lamellae contain capillaries
how are fish adapted for gas exchange?
● many gill filaments that are highly branched with lamellae - increases surface area
● ventilation + blood flow + counter current flow - maintains concentration gradient
● lamellae have thin walls(epithelium) - decreases diffusion distance
what is counter-current flow?
● blood and water flow in opposite directions - through and over the lamellae
● there is a conc gradient maintained along entire lamellae
● O2 conc between water and blood does not reach equilibrium
what is the structure of a leaf?
● waxy cuticle
● upper epidermis - layer of tightly packed cells
● palisade mesophyll layer - layer of elongated cells containing chloroplasts
● spongy mesophyll layer - layer of cells that contains network of air spaces
● stomata - pores (usually) on underside of the leaf which allows air to enter
● guard cells - pairs of cells that control the opening and closing of stomata
● lower epidermis - layer of tightly packed cells
how are leaves dicotyledonous plants adapted to gas exchange
● large surface area - main gas exchange surface are mesophyll cells inside leaf
● when guard cells are turgid (full of water), stoma open allowing air to enter leaf
(opposite of turgid is flaccid)
● air spaces within spongy mesophyll layer allows CO2 to rapidly diffuse into cells
● conc gradient maintained - CO2 is quickly used up in photosynthesis by cells containing chloroplasts
● short diffusion distance - thinness of plant tissues and stomata so no active ventilation is required
what is the formula for photosynthesis
6CO2 + 6H2O –(light)–> C6H12O6 + 6O2
what is the formula for aerobic respiration
C6H12O6 + 6O2 —> 6CO2 + 6H2O
how does H2O enter plant
osmoses into roots
how do minerals enter plant
actively transported into roots
how do plants control water loss
● day: CO2 and O2 diffuse through stomata. H2O lost through transpiration
● night: closed stomata to stop water loss by transpiration. water can not be used in photosynthesis
● waxy cuticle
how are xerophytic plants adapted to reduce transpiration?
● waxy cuticle - increases diffusion distance
● spines of cactus - decreases surface area
● rolled leaf - decreases surface area and conc gradient
● stomata sunken In pits - decreases conc gradient
what is the singular for stomata?
stoma
how do you draw scientific drawings?
● no shading
● label lines need to be parallel
● label lines need to be on one side
● no hanging lines
● no sketched lines
● draw with sharp pencil
● labels with ruler and with pen
● use key for magnification
● add title
● no arrow heads
