gas exchange

• metabolic activity of single celled organism

  low
• what does it mean if metabolic activity is low

  O2 demands and C02 production of the cell is low
• SA:Vol ratio of single celled organism

  high
• metabolic activity of multi-cellular organism

  high
• what does it mean if metabolic activity is high

  O2 demands and C02 production of the cell are high
• SA:Vol ratio of multi-cellular organism

  low
• calculate;ation for SA:Vol ratio

  ratio= SA/Vol
• 4 features of efficient gaseous exchange

  - increased surface area

  -thin layers

  -good blood supply

  -ventilation
• how does increased surface area help gaseous exchange

  provides the area needed for exchange and overcomes the limitations of the SA:Vol ratio of larger organisms
• organisms with increased SA examples

  root hair cells, villi
• where are villi found

  in the small intestine
• how do thin layers help gaseous exchange

  diffusion path is short, the process is fast and efficient
• organs with thin layers examples

  alveoli and the villi
• organs with good blood supply examples

  alveoli, fish gills, villi
• how does a good blood supply help with gaseous exchange

  the steeper the concentration gradient, the faster diffusion takes place. a good blood supply ensures that substances are constantly delivered to and from the exchange surface- this maintains a steep concentration gradient
• how does ventilation help gaseous exchange

  helps to maintain the concentration gradient of gases and makes the process more efficient
• organs with good ventilation examples

  alveoli, fish gills
• human SA:Vol ratio


  small
• human metablic rate


  high- we are very active and have to maintain our body temperature independent of the environment
• how do nasal cavities help with gaseous exchange?

  - have a large SA

  - have good blood supply- warms the air to a body temperature

  - have a wiry lining which secretes mucus to trap dust and bacteria- protect lungs from irritation and infection

  - most surfaces- increase humidity of the air to reduce evaporation from exchange surfaces
• what happens to the air after passing through the nasal cavity?

  the air is the same temperature and humidity as the air already there
• how does the trachea help with gaseous exchange?

  lined with ciliated epithelium cells which have goblet cells between and below them
• what is the trachea


  the main artery which carries clean, warm and moist air from the nose to the chest
• what is the trachea supported by and why?

  incomplete rings of strong, flexible cartilage- to stop the trachea from collapsing
• why are the cartilage rings incomplete in the trachea

  so food can easily move down the oesophagus behind the trachea
• what the the ciliated epithelium cells covered in and why does It help?

  covered in cilia- beat and move mucus away from the lungs (into the throat)
• what stops the cilia from beating


  cigarette smoke
• what do goblet cells do?

  secrete mucus onto the lining of the trachea to trap dust and microorganisms that have escaped the nose lining
• where does the left bronchus lead to

  left lung
• where does the right bronchus lead to

  right lung
• what does the trachea divide to form

  right and left bronchus
• what supports the bronchi?

  smaller rings of supporting cartilage
• what do the bronchi divide into


  bronchioles
• diameter of bronchioles


  1mm or less
• do bronchioles have cartilage rings

  no
• what do bronchioles walls have

  smooth muscle
• what happens when the smooth muscle contracts in the bronchioles

  the bronchioles constrict (close up)- changes the volume of air reaching the lungs
• what happens when the smooth muscle relaxes in the bronchioles

  the bronchioles dilate (open)-changes the volume of air reaching the lungs
• what are the bronchioles lined with that makes gaseous exchange possible?

  thin layer of flattened epithelium cells
• what are alveoli


  tiny air sacs in the lungs