Topic 3

• surface area: volume ratio is an adaption in gas exchange, larger organisms have smaller ratio
• pulmonary ventilation= tidal volume x ventillation rate
• list structure of human gas exchange

  lungs, trachea, bronchi, bronchioles, alveoli
• describe inspiration

  external intercostal muscles contract, pressure rises above atmospheric pressure, lung volume increase, thoracic activity increases
• describe process of expiration

  internal intercostal muscles contract, increasing pressure, decreasing thoracic activity
• what are the 3 advantages for alveolar epithelium

  large surface area for gas exchange

  thin for short diffusion distance

  maintains concentration gradient
• describe structure of gas exchange for insects

  trachea, tracheoles, spiracle
• what is spiracles in insects

  where oxygen and carbon dioxide enter and leave
• method of moving gas in insects

  diffusion creates concentration gradient from tracheoles to the atmosphere
• method of moving gas in insects

  insects contract and relax their muscles to move gases along
• method of moving gas in insects

  when in flight muscles respire aerobically producing lactate which lowers the water potential in cells, so water moves from tracheoles by osmosis. decreases volume in tracheoles so more air from atmosphere drawn in.
• what are adaptations of gas exchange in insects

  large number fine tracheoles for large surface area
• adaptations of gas exchange in insects

  thin walls of tracheoles for short diffusion distance between spiracles and tracheoles
• adaptations for gas exchange in insects

  use oxygen and production of carbon dioxide for steep diffusion gradient
• how do we prevent water loss in gas exchange of insects

  small surface area: volume ratio where insects' water evaporates from

  waterproof exoskeleton

  spiracles can open and close
• diffusion= surface area x difference in concentration/ length of diffusion pathway
• when fish open their mouth water rushes over gills and out of holes inside of their head
• adaptations of fish gas exchange system

  large surface area to volume ratio

  short diffusion distance due to capillary network

  maintaining concentration gradient with countercurrent flow
• what is countercurrent flow

  when water flows over gills in opposite direction to flow of blood in capillaries, ensuring equilibrium is not reached, and ensures diffusion gradient is maintained across entire length gill lamellae
• what is the structure of gas exchange structures in fish

  4 layers of gills made of gill filaments each filament covered by lamellae at right angles, creating a large surface area
• importance of stomata in gas exchange of leaves 


  oxygen diffuses out, carbon dioxide diffuses in, they close at night to reduce water loss by evaporation when no photosynthesis
• what is xerophytic plants and how are they adapted

  adapted to survive with limited water, they have curled leaves and many hairs to increase humidity
• what are cornary arteries

  supply cardiac muscle with oxygenated blood, branch off the aorta. if blocked the cardiac muscle wont receive oxygen therefore wont be able to respire and cells will die (heart attack)
• what is the role of arteries

  carry blood away from the heart
• role of arterioles

  smaller arteries, connected to capillaries
• role of capillaries

  connect arterioles to veins
• role of veins

  carry blood back to heart
• role pulmonary artery

  carry deoxygenated blood from right ventricle to lungs to become oxygenated
• role of aorta

  carries oxygenated blood from left ventricle to rest of body
• role of valves

  prevent backflow of blood so only open when pressure is higher behind the valve
• role of septum

  separates oxygenated and deoxygenated blood. maintains higher concentration of oxygen in oxygenated blood to maintain concentration gradient and enable diffusion to respiring cells.
• describe muscle layer in artery

  thicker than vein so constriction and dilation occurs to control volume of blood
• describe muscular layer in vein

  thin so cant control blood flow
• describe elastic layer in arteries

  thicker than vein to help maintain blood pressure. walls can stretch and recoil in response to heart beat
• describe elastic layer in veins

  thin as the pressure is much lower
• describe wall thickness in arteries

  thicker wall than vein to help prevent bursting due to high pressure
• describe wall thickness in veins

  thin as pressure is much lower so there is low risk of bursting. thinness means vessels can be easily flattened to help flow of blood to the heart
• is there valves in arteries

  no
• is there valves in veins

  yes as there is low pressure
• describe the size of capillaries and why this helps

  narrow diameter to slow blood flow. red blood cells only just fit and they are very squashed against the walls of the capillaries which maximises the diffusion rate