Exchange surfaces:

• Human gas exchange:

  TRACHEA:

  • cartilage rings
  • ciliated epithelium and goblet cells which secrete and waft mucus to prevent dust etc from entering the lungs

  BRONCHUS:

  • cartilage rings
  • ciliated epithelium and goblet cells

  BRONCHIOLES:

  • smooth muscles in walls which constrict etc to control air to lungs

  AVEOLI:

  • elastic fibers for recoiling
  • smooth epithelium cells for gas exchange
• Specialised gas exchange are needed for:

  1. Low SA:V

  • less SA available for absorption of gasses and nutrients

  2. Metabolic activity:

  • high metabolic activity s high O2 demand and CO2 production

  3. Size

  • Multicellular organisms are much bigger so tend to produce more waste products and need for products is high as more cells need to survive.
• Features of specialised exchange surfaces:

  1. Large SA:V (ROOT CELLS)

  • increases SA available for absorption

  2. thin membrane (AVEOLI)

  • provides a short diffusion pathway

  3. Good blood supply: (IE AVEOLI)

  • maintain conc gradient so effective diffusion
• Ventilation in insects:

  Active

  • flying insects need more O2
  • muscles contract to create a pumping movement of air for ventilation
• Inhalation:

  ACTIVE:

  1. Diaphragm contracts

  • Flatterns and lowers

  2. Intercostal muscles contracts and ribs move up and out

  3. V volume of thorax increases, pressure decreases

  4. Pressure outside is greater than pressure in lungs so air is drawn in
• Expiration

  PASSIVE:

  1. Diaphragm relaxes

  • moves up
  • curves

  2. External intercostal muscles relax so ribs move in and down.

  3. Volume of thorax decreases and pressure increases

  4. Pressure outside is less than pressure inside lungs so air is forced out
• Forced expiration:

  ACTIVE:

  1. intercostal internal muscles contract

  • ribs are pulled down and fast

  2. Abdominal muscles contract pushing diaphragm up

  3. Pressure increases rapidly

  4. Air moves out the lungs
• Tracheal system in insects:

  Have impermeable exoskeleton surrounding body so gas exchange cannot occur though it therefore are in need for a specialised gas exchange system.

  1. Opening in exoskeleton called spiracle- air enters insect. Controlled by sphincters to control water loss- keep them closed as much as possible when active
  2. Air enters to trachea- lined with chitin spirals to keep them open - chitin means no gas exchange
  3. Trachea branch to form tracheoles- no chitin so gas exchange occurs now
  4. Tracheoles runs into muscles and tissues so gas is exchanged
• Gas exchange in fish:

  Mechanism

  • counter-current exchange system — blood flows in opposite direction to water so there is a constant diffusion gradient so O2 moves from water to blood

  Gills

  • each gill arch is attached to stacks of gill filaments

  • gill filaments have lamellae on surface rich blood supply, large SA:V
• Ventilation in fish:

  1. Fish open mouth, floor of buccal cavity is lowered
  2. Volume of buccal cavity increases so pressure decreases in cavity
  3. Therefore water flows into buccal cavity from high pressure outside and low pressure inside
  4. Fish raises floor of buccal cavity and closes mouth
  5. So pressure in buccal cavity increases
  6. So water flows from buccal cavity to gill cavity
  7. Pressure starts to build up in gill cavity as water moves in, so operculum is forced open and water can exit the fish
  8. Operculum closes when floor of buccal cavity is lowered at start of next cycle
• Definitions:

  • Vital capacity- max volume of air breathed in or out in 1 breath
  • Tidal volume- volume of air breathed in or out in 1 resting breath
  • Inspiratory reserve volume- max volume of air you can breath in over and above normal volume
  • Expiratory reserve volume- extra amount of air you can force out lungs over and above normal exhalation
• Definitions:

  • Residual volume- volume of air left in lungs after largest possible exhale
  • Total lung capacity- total volume of air which can be held in lungs at given time (residual volume + vital capacity)
  • Breathing rate- breaths in 1 minute
  • Oxygen uptake- volume of 02 used in a given time

  Measure using spirometer

  • breathe normallySoda lime removes the CO2