gas exchange Flashcards
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 fick’s law?
surface area x difference in conc / diffusion distance
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
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
