3.1 EXCHANGE SURFACES AND BREATHING

• Why do multicellular organisms require specialised gas exchange surfaces?

  Their SA:V means the distance that needs to be crossed is larger and substances cannot easily enter the cells as in single celled-organisms
• How is SA:V calculated

  surface area / volume
• Big organisms have a _______ SA:V while small organisms have a ______ SA:V

  - small

  
  

  - large
• Why is diffusion alone enough for single celled organisms

  - metabolic activity is low

  
  

  - SA:V is large
• Features of effective exchange systems

  -increases surface area =root hair cells in plants

  -thin layer =(short distance diffusion) alveoli in the lungs

  -good blood supply/ventilation to maintain gradient=(steeper concentration gradient ) gills and alveoli
• Describe the trachea and its function in the mammalian gaseous exchange system.

  - wide tube supported by C-shaped cartilage to keep the air passage open during pressure changes

  
  

  - lined by ciliated epithelium cells which move mucus produced by goblet cells , cilia moves mucus towards the throat to be swallowed preventing lung infections

  
  

  - carries air to the bronchi
• Describe the bronchi and their function in the mammalian gaseous exchange systems

  - supported by rings of cartilage and are lived by ciliated epithelium cells and goblets cells

  
  

  - they are narrow and there are two made of smooth muscle

  
  

  - allow passage of air into the bronchioles
• Describe the bronchioles and their function in the mammalian gaseous exchange systems

  - narrower than bronchi

  
  

  - no cartilage only smooth muscle and elastic firbres so that they can contract and relax easily during ventilation

  
  

  - allow passage of air into the alveoli
• Describe the alveoli and their function in the mammalian gaseous exchange systems

  - mini air sacs lined with epithelium cells, collagen, elastic fibres

  
  

  - site of gas exchange

  
  

  -walls one cell thick covered with network of capillaries

  
  

  -O2 from alveoli diffuses into bloodstream and CO2 into alveoli
• What is ventilation?

  air moving in and out of lungs because of pressure change in the thorax
• Inspiration (breathing in/ inhalation ) :

  - energy required

  
  

  - external intercostal muscle contracts and ribs move upwards and outwards

  
  

  -diaphragm contracts and becomes flattened and lowers

  
  

  - volume of thorax increases

  
  

  - pressure decreases in lungs

  
  

  -air flows inside lungs up the pressure gradient
• expiration (breathing out / exhalation )

  - passive process

  
  

  - external intercostral muscle relaxed and ribs move downwards and inwards

  
  

  - diaphragm relaxed move upwards

  
  

  - volume of thorax decreases

  
  

  - pressure increases in the lungs

  
  

  - internal intercostral muscle contracts

  
  

  - air flows out of lungs down pressure gradient
• What is used for measuring the volume of air

  - peak flow meter (measures rate air expelled from lungs)

  
  

  - vitalographs (breath as quickly as possible and graph will be produced )

  
  

  - spirometer ( measure volume of air inspired and expired by and individual)
• How to calculated ventilation rate

  tidal volume x breathing rate
• What is tidal volume?

  volume of air that moves in and out of the lungs with each resting breathe
• What is inspiratory reserve volume?

  maximum amount of volume of air you can breathe in over and above a normal inhalation
• What is residual volume?

  volume of air that is left in your lungs when you have exhaled as hard as possible
• What is vital capacity?

  maximum volume of air that can be breathed in and out of the lungs
• What is expiratory reserve volume?

  The extra amount of air you can force out of your lungs over and above the normal tidal volume of air you breathe out
• What is total lung capacity?

  vital capacity + residual volume
• Define breathing rate

  number of breaths taken per minute
• What are the steps of bony fish gaseous exchange

  1 . Fish opens mouth lowering floor of buccal cavity increasing volume and decreasing pressure as water comes in

  
  

  2. Fish closes mouth , buccal cavity rises , increases pressure and decreases volume forcing water to travel to gill fillaments

  
  

  3. Increased pressure in gills area causes operculum on sided to open so water leaves the fish
• Name and describe the main features of a fish's gas transport system.

  -GILL ARCH =support structure of gill , large SA:V , good blood supply and thin layers

  -GILL LAMELLAE= at right angles to theGILL FILLAMENTS, rich blood supply and large SA increasing SA:V , blood and water flow across them in opposite directions (countercurrent)
• How does the counter current exchange systems maximise oxygen absorbed by the fish

  Maintains a steep concentration gradient as water is always next to blood of a lower oxygen concentration

  
  

  keeps rate of diffusion constant
• Explain the process of gas exchange in insects

  1- spiracles open when insect is moving and remains closed when not moving to prevent water loss

  
  

  2- O2 travels down conc gradient to the cells to be released and CO2 travels to spiracles to be removed

  
  

  3- oxygen travels thorugh tracheae (tube lined by spirals of chitin that keep them open if bent or pressed) that divided into tracheoles (no chitin) to diffuse into cells . Both provide :

  - large SA

  - thin = short distance diffusion

  
  

  
  

  tracheal fluid (at end of tracheoles) = limit s penetration of air for diffusion
• What do insects have

  exoskeleton
• Where are the spiracles found ?

  along thorax and abdomen
• insects process 1-> 2-> 3

  1 = SPIRACLES

  
  

  2= TRACHEAE

  
  

  3= TRACHEOLES
• lable

  A) tidal volume

  B) inspiratory reserve volume

  C) residual volume

  D) expiratory reserve volume

  E) vital capacity

  F) total lung capacity

  
• label

  A) inspiration

  B) expiration